bluuebunny/crossref_metadata_2025 huggingface dataset:
The Nature of a Cosmic-Ray Accelerator, CTB 37 B, Observed with Suzaku and Chandra
Authors: Nakamura Ryoko , Bamba Aya , Ishida Manabu , Nakajima Hiroshi , Yamazaki Ryo , Terada Yukikatsu , Pühlhofer Gerd , Wagner Stefan J.
Published: March 2014

We report on Suzaku and Chandra observations of the young supernova remnant CTB 37 B, from which TeV $\gamma$-rays were detected by the H.E.S.S. Cherenkov telescope. The 80 ks Suzaku observation provided us with a clear image of diffuse emission and high-quality spectra. The spectra revealed that the diffuse emission is comprised of thermal and non-thermal components. The thermal component can be represented by an NEI model with a temperature, a pre-shock electron density and an age of 0.9$\pm$0.2 keV, 0.4$\pm$0.1 cm$^{-3}$, and 650$^{+2500}_{-300}$yr, respectively. This suggests that the explosion of CTB 37 B occurred in a low-density space. A non-thermal power-law component was found from the southern region of CTB 37 B. Its photon index of $\sim$1.5 and a high roll-off energy ($>rsim$15 keV) indicate efficient cosmic-ray acceleration. A comparison of this X-ray spectrum with the TeV $\gamma$-ray spectrum leads us to conclude that the TeV $\gamma$-ray emission seems to be powered by either multi-zone Inverse Compton scattering or the decay of neutral pions. The point source resolved by Chandra near the shell is probably associated with CTB 37 B, because of the common hydrogen column density with the diffuse thermal emission. Spectral and temporal characteristics suggest that this source is a new anomalous X-ray pulsar.
Suzaku Observations of M 82 X-1 : Detection of a Curved Hard X-Ray Spectrum
Authors: Miyawaki Ryohei , Makishima Kazuo , Yamada Shin’ya , Gandhi Poshak , Mizuno Tsunefumi , Kubota Aya , Tsuru Takeshi G. , Matsumoto Hironori
Published: March 2014

A report is presented on Suzaku observations of the ultra-luminous X-ray source X-1 in the starburst galaxy M 82, made three times in 2005 October for an exposure of $\sim$30 ks each. The XIS signals from a region of radius 3$^\prime$ around the nucleus defined a 2–10 keV flux of 2.1$\times$10$^{-11}$ergs$^{-1}$cm$^{-2}$ attributable to point sources. The 3.2–10 keV spectrum was slightly more convex than a power-law with a photon index of 1.7. In all observations, the HXD also detected signals from M 82 up to $\sim$20 keV, at a 12-20 keV flux of 4.4$\times$10$^{-12}$ergs$^{-1}$cm$^{-2}$. The HXD spectrum was steeper than that of the XIS. The XIS and HXD spectra can be jointly reproduced by a cutoff power-law model, or similar curved models. Of the detected wide-band signals, 1$/$3 to 2$/$3 are attributable to X-1, while the remainder to other discrete sources in M 82. Regardless of the modeling of these contaminants, the spectrum attributable to X-1 is more curved than a power-law, with a bolometric luminosity of (1.5–3)$\times$10$^{40}$ergs$^{-1}$. These results are interpreted as Comptonized emission from a black hole of 100–200 solar masses, radiating roughly at the Eddington luminosity.
Spectral Transitions of an Ultraluminous X-Ray Source, NGC 2403 Source 3
Authors: Isobe Naoki , Makishima Kazuo , Takahashi Hiromitsu , Mizuno Tsunefumi , Miyawaki Ryouhei , Gandhi Poshak , Kawaharada Madoka , Senda Atsushi , Yoshida Tessei , Kubota Aya , Kobori Hiroshi
Published: March 2014

A Suzaku observation of an ultraluminous X-ray source, NGC 2403 Source 3, performed on 2006 March 16–17, is reported. The Suzaku XIS spectrum of Source 3 was described as multi-color black-body-like emission from an optically thick accretion disk. The innermost disk temperature and radius were measured to be $T_{\rm in}$$=$ 1.08$_{-0.03}^{+0.02}$keV and $R_{\rm in}$$=$ 122.1$_{-6.8}^{+7.7} \ \alpha^{1/2}$km, respectively, where $\alpha$$=$ (cos 60$^\circ /$cos $i$) with $i$ being the disk inclination. Its bolometric luminosity was estimated to be $L_{\rm bol}$$=$ 1.82 $\times$ 10$^{39}\alpha $ergs$^{-1}$. Archival Chandra and XMM-Newton data of the source were analyzed. In almost all observations, the source showed multi-color black-body-like X-ray spectra with parameters similar to those of the Suzaku observation. In only one Chandra observation, however, Source 3 exhibited a power-law-like spectrum, with a photon index of $\Gamma$$=$ 2.37$\pm$0.08, when it was fainter by $\sim$15% than in the Suzaku observation. This behavior is explained in terms of a transition between a slim-disk state and “very high” states, both found in Galactic black hole binaries, when their luminosity apporached the Eddington limit. These results are utilized to argue that ultraluminous X-ray sources generally have significantly higher masses than ordinary stellar-mass black holes.
X-Ray Halo around the Spiral Galaxy NGC 4631 Observed with Suzaku
Authors: Yamasaki Noriko Y. , Sato Kosuke , Mitsuishi Ikuyuki , Ohashi Takaya
Published: March 2014

A Suzaku observation of the edge-on spiral galaxy NGC 4631 confirmed its X-ray halo extending out to about 10 kpc from the galactic disk. The XIS spectra yielded the temperature and metal abundance for the disk and the halo regions. The observed abundance pattern for O, Ne, Mg, Si, and Fe is consistent with the metal yield from type II supernovae, with an O mass of about 10$^{6}M_\odot$ contained in the halo. These features imply that metal-rich gas produced by type II supernova is brought into the halo region very effectively, most likely through a galactic wind. The temperature and metal abundance may be affected by charge exchange and dust. An upper limit for the hard X-ray flux was obtained, corresponding to a magnetic field higher than 0.5$\mu$G.
Hard X-Ray Spectrum from West Lobe of Radio Galaxy Fornax A Observed with Suzaku
Authors: Tashiro Makoto S. , Isobe Naoki , Seta Hiromi , Matsuta Keiko , Yaji Yuichi
Published: March 2014

An observation of the West lobe of radio galaxy Fornax A (NGC 1316) with Suzaku is reported. Since Feigelson et al. (1995, ApJ, 449, L149) and Kaneda et al. (1995, ApJ, 453, L13) discovered the cosmic microwave background boosted inverse-Comptonized (IC) X-rays from the radio lobe, the magnetic field and electron energy density in the lobes have been estimated under the assumption that a single component of the relativistic electrons generates both the IC X-rays and the synchrotron radio emission. However, electrons generating the observed IC X-rays in the 1–10 keV band do not possess sufficient energy to radiate the observed synchrotron radio emission under the estimated magnetic field of a few $\mu$G. On the basis of observations made with Suzaku, we show in the present paper that a 0.7–20 keV spectrum is well described by a single power-law model with an energy index of 0.68 and a flux density of 0.12$\pm$0.01 nJy at 1 keV from the West lobe. The derived multiwavelength spectrum strongly suggests that a single electron energy distribution over a Lorentz factor $\gamma$$=$ 300–90000 is responsible for generating both the X-ray and radio emissions. The derived physical quantities are not only consistent with those reported for the West lobe, but are also in very good agreement with those reported for the East lobe.
Suzaku Observations of Metallicity Distribution in the Intracluster Medium of the NGC 5044 Group
Authors: Komiyama Madoka , Sato Kosuke , Nagino Ryo , Ohashi Takaya , Matsushita Kyoko
Published: March 2014

The metallicity distribution in the intracluster medium of the NGC 5044 group was studied up to 0.3 $r_{180}$ using the XIS instrument aboard the Suzaku satellite. The abundances of O, Mg, Si, S, and Fe were measured with high accuracy. The region within a radius of 0.05 $r_{180}$ from the center shows approximately solar abundances of Mg, Si, S, and Fe, while the O$/$Fe ratio is about 0.5–0.6 in solar units. In the outer region, the Fe abundance gradually drops to 0.3 solar. The radial abundance profiles of Mg, Si and S are similar to that of Fe, while that of O seems to be flatter. At $r$$>$ 0.05 $r_{180}$, the mass density profile of O differs from that of Fe, showing a shoulder-like structure that traces the luminosity density profile of galaxies. The mass-to-light ratios for O and Fe in NGC 5044 are one of the largest among groups of galaxies, but they are still smaller than those in rich clusters. These abundance features probably reflect the metal enrichment history of this relaxed group hosting a giant elliptical galaxy in the center.
Suzaku Observation of Group of Galaxies NGC 507: Temperature and Metal Distributions in the Intra-Cluster Medium
Authors: Sato Kosuke , Matsushita Kyoko , Ishisaki Yoshitaka , Yamasaki Noriko Y. , Ishida Manabu , Ohashi Takaya
Published: March 2014

The temperature and abundance distributions of the intra-cluster medium (ICM) in the NGC 507 group of galaxies were studied with Suzaku. The observed concentric annular spectra were well-represented by a two-temperature model for ICM, and steeper abundance gradients were found for Mg, Si, S, and Fe compared with O in the central region. The abundance ratios of $\alpha$-elements to iron were found to be similar to those in other groups and poor clusters. We calculated the metal mass-to-light ratios for Fe, O, and Mg (IMLR, OMLR, MMLR) for NGC 507, and values for different systems were compared. Hotter and richer systems tend to show higher values of IMLR, OMLR, and MMLR. OMLR and MMLR were measured to an outer region for the first time with Suzaku, while IMLR was consistent with that with ASCA. We also looked into a 2-dimensional map of the hardness ratio, but found no significant deviation from circular symmetry.
Temperature and Metallicity in the Intra-Cluster Medium of Abell 262 Observed with Suzaku
Authors: Sato Kosuke , Matsushita Kyoko , Gastaldello Fabio
Published: March 2014

We studied the temperature and abundance distributions of the intra-cluster medium (ICM) in the Abell 262 cluster of galaxies observed with Suzaku. Abell 262 is a bright, nearby poor cluster with an ICM temperature of $\sim$2 keV, thus providing useful information about the connection of ICM properties between groups and clusters of galaxies. With the XIS instrument, we directly measured not only the Si, S, and Fe lines, but also the O and Mg lines, and obtained those abundances to an outer region of $\sim$ 0.43$r_{180}$ for the first time. We found steep gradients for Mg, Si, S, and Fe abundances, while O showed an almost flat abundance distribution. The abundance ratios of $\alpha$-elements to Fe were found to be similar to those of the other clusters and groups. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 3.0$\pm$0.6 within 0.1$r_{180}$; the value was consistent with those for other clusters and groups. We also calculated the metal mass-to-light ratios (MLRs) for Fe, O, and Mg with $B$-band and $K$-band luminosities of the member galaxies of Abell 262. The derived MLRs were comparable to those for other clusters with $kT$$=$ 3–4 keV.
New CTI Correction Method for Spaced-Row Charge Injection of the Suzaku X-Ray Imaging Spectrometer
Authors: Uchiyama Hideki , Ozawa Midori , Matsumoto Hironori , Tsuru Takeshi Go , Koyama Katsuji , Kimura Masashi , Uchida Hiroyuki , Nakajima Hiroshi , Hayashida Kiyoshi , Tsunemi Hiroshi , Mori Hideyuki , Bamba Aya , Ozaki Masanobu , Dotani Tadayasu , Takei Dai , Murakami Hiroshi , Mori Koji , Ishisaki Yoshitaka , Kohmura Takayoshi , Prigozhin Gregory , Kissel Steve , Miller Eric D. , LaMarr Beverly , Bautz Marshall
Published: March 2014

The charge transfer inefficiency (CTI) of the X-ray CCDs aboard the Suzaku satellite (X-ray Imaging Spectrometers: XIS) has increased since the launch due to radiation damage, and the energy resolution has been degraded. To improve the CTI, we have applied a spaced-row charge injection (SCI) technique to the XIS in orbit; by injecting charges into CCD rows periodically, the CTI is actively decreased. The CTI in the SCI mode depends on the distance between a signal charge and a preceding injected row, and the pulse height shows periodic positional variations. Using in-flight data of onboard calibration sources and of the strong iron line from the Perseus cluster of galaxies, we studied the variation in detail. We developed a new method to correct the variation. By applying the new method, the energy resolution (FWHM) at 5.9 keV in 2008 March is $\sim$155 eV for the front-illuminated CCDs and $\sim$175 eV for the back-illuminated CCD.
X-Ray Studies of HESS J1809–193 with Suzaku
Authors: Anada Takayasu , Bamba Aya , Ebisawa Ken , Dotani Tadayasu
Published: March 2014

Suzaku observed the region including HESS J1809$-$193, a TeV unidentified source, and confirmed the existence of extended hard X-ray emission previously reported by ASCA, as well as hard X-ray emission from PSR J1809$-$1917 in this region. A one-dimensional profile of the diffuse emission is represented along with a Gaussian model with a best-fit $\sigma$ of 7$^\prime \pm$ 1$^\prime$. The diffuse emission extends for at least 21 pc (at the 3$\sigma$ level, assuming a distance of 3.5 kpc), and has a hard spectrum with a photon index of $\Gamma \sim$ 1.7. The hard spectrum suggests a pulsar wind nebula origin, which is also strengthened by the hard X-ray emission from PSR J1809$-$1917, itself. Thanks to the low background of Suzaku XIS, we were able to investigate the spatial variation of the energy spectrum, but no systematic spectral change in the extended emission was found. These results imply that the X-ray emitting pulsar wind electrons can travel up to 21 pc from the pulsar without any noticeable energy loss via synchrotron emission.
Warm and Dense Molecular Gas in the N 159 Region: 12CO J = 4–3 and 13CO J = 3–2 Observations with NANTEN2 and ASTE
Authors: Mizuno Yoji , Kawamura Akiko , Onishi Toshikazu , Minamidani Tetsuhiro , Muller Erik , Yamamoto Hiroaki , Hayakawa Takahiro , Mizuno Norikazu , Mizuno Akira , Stutzki Jürgen , Pineda Jorge L. , Klein Uli , Bertoldi Frank , Koo Bon-Chul , Rubio Monica , Burton Michael , Benz Arnold , Ezawa Hajime , Yamaguchi Nobuyuki , Kohno Kotaro , Hasegawa Tetsuo , Tatematsu Ken’ichi , Ikeda Masafumi , Ott Jürgen , Wong Tony , Hughes Annie , Meixner Margaret , Indebetouw Remy , Gordon Karl D. , Whitney Barbara , Bernard Jean-Philippe , Fukui Yasuo
Published: March 2014

New $^{12}$CO $J =$ 4–3 and $^{13}$CO $J =$ 3–2 observations of the N 159 region, an active site of massive star formation in the Large Magellanic Cloud, have been made with the NANTEN2 and ASTE submillimeter telescopes, respectively. The $^{12}$CO $J =$ 4–3 distribution is separated into three clumps, each associated with N 159 W, N 159 E, and N 159 S. These new measurements toward the three clumps are used in coupled calculations of molecular rotational excitation and line radiation transfer, along with other transitions of the $^{12}$CO $J =$ 1–0, $J =$ 2–1, $J =$ 3–2, and $J =$ 7–6 as well as the isotope transitions of $^{13}$CO $J =$ 1–0, $J =$ 2–1, $J =$ 3–2, and $J =$ 4–3. The $^{13}$CO $J =$ 3–2 data were newly taken for the present work. The temperatures and densities were found to be $\sim$70&x2013;80 K and $\sim$3 $\times$ 10$^{3}$cm$^{-3}$ in N 159 W and N 159 E, and $\sim$30 K and $\sim$1.6 $\times$ 10$^{3}$cm$^{-3}$ in N 159 S. These results were compared with the star-formation activity based on data of young stellar clusters and HII regions as well as midinfrared emission obtained with the Spitzer MIPS. The N 159 E clump is associated with cluster(s) embedded, as observed at 24$\mu$m by the Spitzer MIPS, and the derived high temperature, 80 K, is interpreted as being heated by these sources. The N 159 E clump is likely to be responsible for a dark lane in a large H II region by dust extinction. On the other hand, the N 159 W clump is associated with clusters embedded mainly toward the eastern edge of the clump only. These clusters show offsets of 20${}^{\prime\prime}$–40${}^{\prime\prime}$ from the $^{12}$CO $J =$ 4–3 peak, and are probably responsible for heating indicated by the derived high temperature, 70 K. The N 159 W clump exhibits no sign of star formation toward the $^{12}$CO $J =$ 4–3 peak position and its western region that shows enhanced $R_{4-3/1-0}$ and $R_{3-2/1-0}$ ratios. We therefore suggest that the N 159 W peak represents a pre-star-cluster core of $\sim$10$^{5} M_{\odot}$ which deserves further detailed studies. The N 159 S clump shows little sign of star formation, as is consistent with the lower temperature, 30 K, and has a somewhat lower density than N 159 W and N 159 E. The N 159 S clump is also a candidate for future star formation.
SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk
Authors: Deguchi Shuji , Nakashima Jun-ichi , Zhang Yong , Chong Selina S. N. , Koike Kazutaka , Kwok Sun
Published: March 2014

We present the results of radio observations of red supergiants in a star cluster, Stephenson (1990, AJ, 99, 1867)’s #2, and of candidates for red supergiants in three star clusters, Mercer et al. (2005, ApJ, 635, 560)’s #4, #8, and #13, in the SiO and H$_2$O maser lines. The Stephenson’s #2 cluster and nearby aggregation at the southwest contain more than 15 red supergiants. We detected one red supergiant at the center of Stephenson’s #2 and three in a southwest aggregation in the SiO maser line; three out of these four were also detected in the H$_2$O maser line. The average radial velocity of the four detected objects is 97 km s$^{-1}$, giving a kinematic distance of 5.5 kpc, which locates this cluster near the base of the Scutum–Crux spiral arm. We also detected six SiO emitting objects associated with other star clusters. In addition, mapping observations in the CO $J =$ 1–0 line toward these clusters revealed that an appreciable amount of molecular gas still remains around the Stephenson’s #2 cluster in contrast to the prototypical red-supergiant cluster, Bica et al. (2003, A&A, 404, 223)’s #122. This indicates that the time scale of gas expulsion differs considerably in individual clusters.
Japanese VLBI Network Mapping of SiO v = 3 J = 1–0 Maser Emission in W Hydrae
Authors: Imai Hiroshi , Nakashima Jun-ichi , Deguchi Shuji , Yamauchi Aya , Nakagawa Akiharu , Nagayama Takumi
Published: March 2014

We report first on two-epoch mapping observations of SiO $v =$ 3 $J =$ 1–0 maser emission in the semiregular variable W Hydrae using the Japanese VLBI Network. The flux density of the $v =$ 3 $J =$ 1–0 emission detected on 2009 February 28 was two orders of magnitude smaller than those of the $v =$ 1 and $v =$ 2 emissions, while a month and half later the $v =$ 3 flux density suddenly increased by a factor of $\sim $25. In contrast, the $v =$ 1 and $v =$ 2 flux densities decreased during this period, as expected from the optical light curve. At the first epoch, the $v =$ 3 maser features were located inside of a ring composed of the $v =$ 1 and $v =$ 2 features by 6 mas ($\gtrsim $0.5 AU) toward the central star. These offsets are meaningfully larger than the error of the fitted ring radius and the difference in the ring sizes of $v =$ 1 and $v =$ 2 masers ($\lesssim $0.2 AU). The present result at the first epoch suggests that $v =$ 3 $J =$ 1–0 SiO masers are predominantly excited in a pumping mechanism (e.g., collisional pumping) different from that recently proposed on the basis of the line overlap with infrared H$_{2}$O lines. Interestingly, the second-epoch observation revealed that the $v =$ 3 features were located on almost the same ring as the $v =$ 2 ring, which is consistent with what line-overlap theory suggests.
Spectral-Lag Relations in GRB Pulses Detected with HETE-2
Authors: Arimoto Makoto , Kawai Nobuyuki , Asano Katsuaki , Hurley Kevin , Suzuki Motoko , Nakagawa Yujin E. , Shimokawabe Takashi , Pazmino Nicolas Vasquez , Sato Rie , Matsuoka Masaru , Yoshida Atsumasa , Tamagawa Toru , Shirasaki Yuji , Sugita Satoshi , Takahashi Ichiro , Atteia Jean-Luc , Pelangeon Alexandre , Vanderspek Roland , Graziani Carlo , Prigozhin Gregory , Villasenor Joel , Jernigan J. Garrett , Crew Geoffrey B. , Sakamoto Takanori , Ricker George R. , Woosley Stanford E. , Butler Nat , Levine Alan , Doty John P. , Donaghy Timothy Q. , Lamb Donald Q. , Fenimore Edward , Galassi Mark , Boer Michel , Dezalay Jean-Pascal , Olive Jean-François , Braga João , Manchanda Ravi , Pizzichini Graziella
Published: March 2014

Using a pulse-fit method, we investigated the spectral lags between the traditional gamma-ray band (50–400 keV) and the X-ray band (6–25 keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB 030528, GRB 040924, GRB 041006, and GRB 050408), detected with the WXM and FREGATE instruments aboard the HETE-2 satellite. We found several relations for individual GRB pulses between the spectral lag and other observables, such as the luminosity, pulse duration, and peak energy, $E_{\rm peak}$. The obtained results are consistent with those for BATSE, indicating that the BATSE correlations are still valid at lower energies (6–25 keV). Furthermore, we found that the photon energy dependence for the spectral lags can be reconciled with the simple curvature effect model. We discuss the implications of these results from various points of view.
Excitation of Trapped g-Mode Oscillations in Warped Disks around Black Holes
Authors: Oktariani Finny , Okazaki Atsuo T. , Kato Shoji
Published: March 2014

In order to study the origin of high-frequency quasi-periodic oscillations observed in X-ray binaries, Kato (2004) suggested a resonant excitation mechanism of disk oscillations in deformed disks. In this paper, we investigate numerically, following his formulation, whether trapped g-mode oscillations in a warped disk, where the warp amplitude varies with the radius, can be excited by this mechanism. For simplicity, we adopt Newtonian hydrodynamic equations with relativistic expressions for the characteristic frequencies of disks. We also assume that the accretion disk is isothermal. We find that the fundamental modes of trapped g-mode oscillations with eigenfrequencies close to the maximum of epicyclic frequency are excited. The intermediate oscillations found are isolated in a narrow region around the resonance radius. After varying some parameters, we find that the growth rate increases as the warp amplitude or the black-hole spin parameter increases, while it decreases as the sound speed increases.
Molecular Clouds as Cosmic-Ray Barometers
Authors: Casanova Sabrina , Aharonian Felix A. , Fukui Yasuo , Gabici Stefano , Jones David I. , Kawamura Akiko , Onishi Toshikazu , Rowell Gavin , Sano Hidetoshi , Torii Kazufumi , Yamamoto Hiroaki
Published: March 2014

The advent of high sensitivity, high resolution $\gamma$-ray detectors, together with a knowledge of the distribution of the atomic hydrogen and especially of the molecular hydrogen in the Galaxy on a subdegree scale, creates a unique opportunity to explore the flux of cosmic rays in the Galaxy. We here present the new data on the distribution of the molecular hydrogen from a large region of the inner Galaxy obtained by the NANTEN Collaboration. We then introduce a methodology which aims to provide a test bed for current and future $\gamma$-ray observatories to explore the cosmic-ray flux at various positions in our Galaxy. In particular, for a distribution of molecular clouds, as provided by the NANTEN survey, and local cosmic-ray density as measured at the Earth, we estimate the expected GeV to TeV $\gamma$-ray signal, which can then be compared with observations, and use to test the cosmic-ray flux.
The Abundance Pattern of O, Ne, Mg, and Fe in the Interstellar Medium of S0 Galaxy NGC 4382 Observed with Suzaku
Authors: Nagino Ryo , Matsushita Kyoko
Published: March 2014

We derived the O, Ne, Mg, and Fe abundances in the interstellar medium (ISM) of a relatively isolated S0 galaxy, NGC 4382, observed with the Suzaku XIS instruments, and compared the O/Ne/Mg/Fe abundance pattern with that of the ISM in elliptical galaxies. The derived temperature and Fe abundance in the ISM are $\sim$ 0.3 keV and 0.6–2.9 solar, respectively. The abundance ratios are derived with considerable accuracy than the abundances, themselves; that is, the O$/$Fe, Ne$/$Fe, and Mg$/$Fe ratios are 0.3, 0.7, and 0.6 in solar units, respectively. The O$/$Fe ratio is smaller than those of the ISM in elliptical galaxies (NGC 720, NGC 1399, NGC 1404, and NGC 4636) observed with Suzaku. Since O, Ne, and Mg are predominantly synthesized by supernovae (SNe) of type II, the observed abundance pattern indicates that the contribution of SN Ia products is higher in the S0 galaxy than in the elliptical galaxy. Since the hot ISM in early-type galaxies is an accumulation of stellar mass and SN Ia products, the low O$/$Fe ratio in the ISM of NGC 4382 reflects a higher rate of present SNe Ia, or stars containing more SN Ia products than those in elliptical galaxies.
Suzaku Observation of the Southeastern Rim of the Cygnus Loop
Authors: Kosugi Hiroko , Tsunemi Hiroshi , Katsuda Satoru , Uchida Hiroyuki , Kimura Masashi
Published: March 2014

X-ray measured metal abundances of the rim of the Cygnus Loop are known to have two patterns. One, seen at narrow regions along the outermost edge, is 0.5-times the solar value, and the other, seen in the remainder of the rim, is 0.2-times the solar value. While the former is “normal”, as the ISM around the Cygnus Loop, the latter is unexpectedly depleted, and its origin has been puzzling. We have been tackling this issue by observing the rims with X-ray observatories. So far, the normal abundance was observed only at regions where no cloud-shock interactions are suggested. On the contrary, based on our recent Suzaku observations, we find the normal abundance at the southeastern rim where cloud-shock interactions are evident. The spatial variation of the abundance there is similar to that in other normal abundance rims: the normal abundance is present along the outermost edge (4$^\prime$ width regions), while the inner region shows strongly depleted abundances. This structure has been confirmed both by the plasma model fit and by the model-free fit. We noticed that the rim regions showing normal abundance correspond to those with a relatively weak radio intensity. Since the Cygnus Loop is believed to be the result of a cavity explosion, we discuss that the abundance distribution is due to the abundance difference between the cavity wall and its outside. The origin of the depleted abundance still remains an open question.
Optical and Near-Infrared Photometry of Nova V2362 Cyg: Rebrightening Event and Dust Formation
Authors: Arai Akira , Uemura Makoto , Kawabata Koji S. , Maehara Hiroyuki , Nakajima Kazuhiro , Kiyota Seiichiro , Kato Taichi , Ohsugi Takashi , Yamashita Takuya , Isogai Mizuki , Nagae Osamu , Chiyonobu Shingo , Fukazawa Yasushi , Mizuno Tsunefumi , Katagiri Hideaki , Takahashi Hiromitsu , Okita Kiichi , Yoshida Michitoshi , Yanagisawa Kenshi , Sato Shuji , Kino Masaru , Kitagawa Masahiro , Sadakane Kozo
Published: March 2014

We present optical and near-infrared (NIR) photometry of a classical nova, V2362 Cyg ($=$ Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening during the period between 100 and 240 d after the maximum of the nova. Our multicolor observation indicates the emergence of a pseudophotosphere with an effective temperature of $\sim\ $9000 K at the rebrightening maximum. After the rebrightening maximum, the object showed a slow fading homogeneously in all of the used bands for one week. This implies that the fading soon after the rebrightening maximum ($\lesssim\ $1 week) was caused by a slowly shrinking pseudophotosphere. Then, the NIR flux drastically increased, while the optical flux steeply declined. The optical and NIR fluxes were consistent with blackbody radiation with a temperature of $\sim\ $1500 K during this NIR rising phase. These facts are likely to be explained by dust formation in the nova ejecta. Assuming an optically thin case, we estimated the dust mass to be 10$^{-10}$–10$^{-8}\ M_{\odot}$, which is less than those in typical dust-forming novae. These results support the senario that a second, long-lasting outflow which caused the rebrightening interacted with a fraction of the initial outflow and formed dust grains.
Internal Fine Structure of Ellerman Bombs
Authors: Hashimoto Yuki , Kitai Reizaburo , Ichimoto Kiyoshi , UeNo Satoru , Nagata Shin’ichi , Ishii Takako T. , Hagino Masaoki , Komori Hiroyuki , Nishida Keisuke , Matsumoto Takuma , Otsuji Kenichi , Nakamura Tahei , Kawate Tomoko , Watanabe Hiroko , Shibata Kazunari
Published: March 2014

We conducted coordinated observations of Ellerman bombs (EBs) between Hinode Satellite and Hida Observatory (HOP12). Ca II H broad-band filter images of NOAA 10966 on 2007 August 9 and 10 were obtained with the Solar Optical Telescope (SOT) aboard the Hinode Satellite, and many bright points were observed. We identified a total of 4 bright points as EBs, and studied the temporal variation of their morphological fine structures and spectroscopic characteristics. With high-resolution Ca II H images of SOT, we found that the EBs, thus far thought of as single bright features, are composed of a few of fine subcomponents. Also, by using Stokes $I$/$V$ filtergrams with Hinode/SOT, and Ca II H spectroheliograms with Hida/Domeless Solar Telescope (DST), our observation showed: (1) The mean duration, the mean width, the mean length, and the mean aspect ratio of the subcomponents were 390 s, 170 km, 450 km, and 2.7, respectively. (2) Subcomponents started to appear on the magnetic neutral lines, and extended their lengths from the original locations. (3) When the Ca II H line of EBs showed the characteristic blue asymmetry, they are associated with the appearance or re-brightening of subcomponents. Summarizing our results, we obtained an observational view that elementary magnetic reconnections take place one by one successively and intermittently in EBs, and that their manifestation is the fine subcomponents of the EB phenomena.
Time Variability of the Geocoronal Solar-Wind Charge Exchange in the Direction of the Celestial Equator
Authors: Ezoe Yuichiro , Ebisawa Ken , Yamasaki Noriko Y. , Mitsuda Kazuhisa , Yoshitake Hiroshi , Terada Naoki , Miyoshi Yoshizumi , Fujimoto Ryuichi
Published: March 2014

We report on the detection of a time variable OVII line emission in a deep 100 ks Suzaku X-ray Imaging Spectrometer spectrum of the galactic ridge X-ray emission. The observed line intensity is too strong (11$\ \pm\ $2 line unit or photon cm$^{-2}\ $s$^{-1}\ $sr$^{-1}\ $) to be emitted inside the heavily obscured galactic disk. It showed a factor of two time variation that showed a significant ($\sim\ $4$\ \sigma$) correlation with the solar-wind O$^{7+}$ ion flux. The high line intensity and good time correlation with the solar wind strongly suggests that it originated from geocoronal solar-wind charge-exchange emission. We discuss the X-ray line intensity while considering a line-of-sight direction and also theoretical distribution models of the neutral hydrogen and solar wind around Earth. Our results indicate that X-ray observations of geocoronal solar-wind charge-exchange emission can be used to constrain these models.
Generation of Alfvén Waves by Magnetic Reconnection
Authors: Kigure Hiromitsu , Takahashi Kunio , Shibata Kazunari , Yokoyama Takaaki , Nozawa Satoshi
Published: March 2014

In this paper, the results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, a guide field. The angle $\theta$ between the magnetic field lines in two half regions was a key parameter in our simulations, whereas the initial distribution of the plasma was assumed to be simple; the density and pressure were uniform, except for the current sheet region. Alfvén waves were generated at the reconnection point and propagated along the reconnected field line. The energy fluxes of the Alfvén waves and the magneto-acoustic waves (slow mode and fast mode) generated by magnetic reconnection were measured. Each flux shows a similar time evolution independent of $\theta$. The percentages of the energies (time integral of energy fluxes) carried by the Alfvén waves and magneto-acoustic waves to the released magnetic energy were calculated. The Alfvén waves carry 38.9%, 36.0%, and 29.5% of the released magnetic energy at the maximum ($\theta =$ 80$^\circ$) in the cases of $\beta =$ 0.1, 1, and 20, respectively, where $\beta$ is the plasma $\beta$ (the ratio of gas pressure to magnetic pressure). The magneto-acoustic waves carry 16.2% ($\theta =$ 70$^\circ$), 25.9% ($\theta =$ 60$^\circ$), and 75.0% ($\theta =$ 180$^\circ$) of the energy at the maximum. Implications of these results for solar coronal heating and acceleration of high-speed solar wind are discussed.
Redshifts of Distant Blazars Limited by Fermi and VHE γ-Ray Observations
Authors: Yang Jianping , Wang Jiancheng
Published: March 2014

Our goal is to limit the redshifts of three blazars, PG 1553$+$113, 3C 66A, and PKS 1424$+$240, through an investigation of their Fermi and VHE (very high energy) $\gamma$-ray observations. We assume that the intrinsic spectra of PG 1553$+$113, 3C 66A, and PKS 1424$+$240 have no cutoff across the Fermi and VHE $\gamma$-ray energy ranges. The intrinsic spectra of VHE $\gamma$-rays are obtained through extrapolation of the Fermi spectra. Comparing the measured and intrinsic VHE spectra due to extragalactic background light (EBL) absorption, we give the redshift upper limits of three blazars, while assuming a specific EBL model. The redshift upper limits of PG 1553$+$113, 3C 66A, and PKS 1424$+$240 are 0.78, 0.58, and 1.19, respectively. Near to the TeV energy the optical depth of VHE $\gamma$ photons might be overestimated by the Franceschini EBL model (Franceschini et al. 2008, A&A, 487, 837), or the second emission component might be present in the VHE spectra and lead the intrinsic photon index to be harder than the Fermi ones.
Suzaku Observation of the Anomalous X-Ray Pulsar 1E 1841−045
Authors: Morii Mikio , Kitamoto Shunji , Shibazaki Noriaki , Kawai Nobuyuki , Arimoto Makoto , Ueno Masaru , Kohmura Takayoshi , Terada Yukikatsu , Yamauchi Shigeo , Takahashi Hiromitsu
Published: March 2014

We report on the results of a Suzaku observation of the anomalous X-ray pulsar (AXP) 1E 1841$-$045 at the center of the supernova remnant Kes 73. We confirmed that the energy-dependent spectral models obtained by previous separate observations were also satisfied over a wide energy range from 0.4 to $\sim$70 keV, simultaneously. Here, the models below $\sim$10 keV were a combination of blackbody (BB) and power-law (PL) functions, or of two BBs with different temperatures at 0.6–7.0 keV (Morii et al. 2003, PASJ, 55, L45), and that above $\sim$20 keV was a PL function (Kuiper et al. 2004, ApJ, 613, 1173). The combination BB $+$ PL $+$ PL was found to best represent the phase-averaged spectrum. Phase-resolved spectroscopy indicated the existence of two emission regions, one with a thermal and the other with a non-thermal nature. The combination BB $+$ BB $+$ PL was also found to represent the phase-averaged spectrum well. However, we found that this model is physically unacceptable due to an excessively large area of the emission region of the blackbody. Nonetheless, we found that the temperatures and radii of the two blackbody components showed moderate correlations in the phase-resolved spectra. The fact that the same correlations have been observed between the phase-averaged spectra of various magnetars (Nakagawa et al. 2009, PASJ, 61, 109) suggests that a self-similar function can approximate the intrinsic energy spectra of magnetars below $\sim$10 keV.
A Detailed Observational Study of Molecular Loops 1 and 2 in the Galactic Center
Authors: Torii Kazufumi , Kudo Natsuko , Fujishita Motosuji , Kawase Tokuichi , Yamamoto Hiroaki , Kawamura Akiko , Mizuno Norikazu , Onishi Toshikazu , Mizuno Akira , Machida Mami , Takahashi Kunio , Nozawa Satoshi , Matsumoto Ryoji , Fukui Yasuo
Published: March 2014

Fukui et al. (2006, Science, 314, 106) discovered two huge molecular loops in the galactic center located at ($l, b$) $\simeq$ (355$^\circ$–359$^\circ$, 0$^\circ$–2$^\circ$) in a large velocity range of $-$180—40 km s$^{-1}$. Following the discovery, we present detailed observational properties of the two loops based on NANTEN $^{12}$CO ($J =$ 1–0) and $^{13}$CO ($J =$ 1–0) datasets at 10 pc resolution, including a complete set of velocity channel distributions and comparisons with HI and dust emissions as well as with the other broad molecular features. We have found new features on smaller scales in the loops, including helical distributions in the loop tops and vertical spurs. The loops have counterparts of the HI gas, indicating that the loops include atomic gas. The IRAS far-infrared emission is also associated with the loops, and was used to derive an X-factor of 0.7 ($\pm$ 0.1) $\times$ 10$^{20}\ $cm$^{-2}$ (K km s$^{-1}$)$^{-1}$ to convert the $^{12}$CO intensity into the total molecular hydrogen column density. From the $^{12}$CO, $^{13}$CO, HI, and dust datasets we estimated the total mass of loops 1 and 2 to be $\sim\ $1.4 $\times$ 10$^6$$M_\odot$ and $\sim\ $1.9 $\times$ 10$^6$$M_\odot$, respectively, where the HI mass corresponds to $\sim\ $10%–20% of the total mass and the total kinetic energy of the two loops is $\sim\ $10$^{52}\ $erg. An analysis of the kinematics of the loops yields that the loops are rotating at $\sim\ $47 km s$^{-1}$ and expanding at $\sim\ $141 km s$^{-1}$ at a radius of $\sim\ $670 pc from the center. Fukui et al. (2006) presented a model that the loops are created by magnetic flotation due to the Parker instability with an estimated magnetic field strength of $\sim\ $150$\ \mu$G. We present comparisons with the recent numerical simulations of the magnetized nuclear disk by Machida et al. (2009, PASJ, 61, 411) and Takahashi et al. (2009, PASJ, 61, 957), and show that the theoretical results are in good agreement with the observations. The helical distributions also suggest that some magnetic instability plays a role similarly to the solar helical features.
On the Rebrightenings of Classical Novae during the Early Phase
Authors: Tanaka Jumpei , Nogami Daisaku , Fujii Mitsugu , Ayani Kazuya , Kato Taichi
Published: March 2014

We report on the spectral evolution of 6 classical novae (V1186 Sco, V2540 Oph, V4745 Sgr, V5113 Sgr, V458 Vul, and V378 Ser), based on low-resolution spectra obtained at the Fujii-Bisei Observatory and the Bisei Astronomical Observatory, Japan. In the light curves, these 6 novae show several rebrightenings during the early phase lasting $\sim\ $10 d after the first maximum in fast novae, and $\sim\ $100 d in slow novae. The early spectra of all of these novae had emission lines with a P-Cygni profile at the maximum brightness. The absorption component of the P-Cygni profiles then disappeared after the maximum, and reappeared when the novae brightened to the next maximum. We suggest that the re-appearance of the absorption component at the rebrightening can be attributable to a re-expansion of the photosphere after it once shifts sufficiently inside. From the light curves, we found that the time intervals of the rebrightenings of these 6 novae show a similar systematic trend, which is applicable to all types of novae; fast and slow, and Fe II type and hybrid type. Moreover, we note the difference between the spectra at the rebrightenings during the early phase and at the rebrightening in V2362 Cyg, and at the oscillation during the transition phase in V1494 Aql, which means a difference in the physical mechanism of the rebrightening during the early phase and the later oscillations.
Astrometry of the Star-Forming Region IRAS 05137+3919 in the Far Outer Galaxy
Authors: Honma Mareki , Hirota Tomoya , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kobayashi Hideyuki , Kurayama Tomoharu , Sato Katsuhisa
Published: March 2014

We present the results of astrometric observations with VERA toward H$_2$O maser sources in IRAS 05137$+$3919, which is thought to be located in the far outer Galaxy. We derived a parallax of $\pi$$=$ 0.086$\ \pm\ $0.027 mas, which corresponds to a source distance of $D$$=$ 11.6$^{+5.3}_{-2.8}\ $kpc. Although the parallax measurement was only at the 3-$\sigma$ level, and thus the distance uncertainty was considerably large, we can strongly constrain the minimum distance to this source, locating the source at a distance from the Sun greater than 8.3 kpc (or 16.7 kpc from the Galaxy's center) at the 90% confidence level. Our results provide an astrometric confirmation that this source is located in the far outer Galaxy beyond 15 kpc from the Galaxy center, indicating that IRAS 05137$+$3919 is one of the most distant star-forming regions from the Galaxy center.
First Detection of Ar-K Line Emission from the Cygnus Loop
Authors: Uchida Hiroyuki , Tsunemi Hiroshi , Tominaga Nozomu , Katsuda Satoru , Kimura Masashi , Kosugi Hiroko , Takahashi Hiroaki , Takakura Satoru
Published: March 2014

We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32 pointings) between 2002 and 2008. The total effective exposure time is 670.2 ks. By using all of the available data, we intended to improve a signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra obtained by the XIS and the EPIC show some line features around 3 keV that are attributed to the S He$\beta$ and Ar He$\alpha$ lines, respectively. Since the Cygnus Loop is an evolved ($\sim\ $ 10000 yr) supernova remnant whose temperature is relatively low ($\lt\ $ 1 keV) compared with other young remnants, its spectrum is generally faint above 3.0 keV, no emission lines, such as the Ar-K line, have ever been detected. The detection of the Ar-K line is the first time, and we found that its abundance is significantly higher than that of the solar value: 9.0$^{+4.0}_{\-3.8}$ and 8.4$^{+2.5}_{\-2.7}$ (in units of solar), estimated from the XIS and the EPIC spectra, respectively. We conclude that the Ar-K line originated from the ejecta of the Cygnus Loop. Follow-up X-ray observations to tightly constrain the abundances of Ar-rich ejecta will be useful to accurately estimate the progenitor's mass.
Penetration Factor for Nuclear Fusion Reaction in Nonthermal Astrophysical Plasmas
Authors: Ki Dai-Han , Jung Young-Dae
Published: March 2014

The nonthermal effects on the nuclear fusion reaction process are investigated in Lorentzian astrophysical plasmas. The closed expression of the classical turning point in Lorentzian plasmas is obtained by the Lambert $W$-function. Using the WKB analysis with the effective screening length, the closed expressions of the fusion penetration factor and the cross section for the nuclear fusion reaction in Lorentzian plasmas are obtained as functions of the spectral index, relative kinetic energy, and plasma parameters. It is shown that the nonthermal character of the Lorentzian plasma enhances the fusion penetration factor. In addition, the nonthermal effect on the penetration factor is found to be more significant in plasmas with higher densities. It would be expected that the fusion reaction rates of the $p$–$p$ chain and the CNO cycle in nonthermal plasmas are always greater than those in thermal Maxwellian plasmas.
Helicity Injection Fluxes of Twist and Writhe
Authors: Yamamoto Tetsuya T.
Published: March 2014

We consider helicity flux equations proposed by previous authors and offer interpretations of these helicity injection equations with twist and writhe. At first, comparing Pariat’s helicity flux equation (2005, A&A, 439, 1191) with Longcope’s (2007, ApJ, 668, 571), we find that the Pariat’s helicity injection equation shows helicity evolution of continuous magnetic field lines, which is an extreme case of the Longcope’s multiple flux tube model. Next, we investigated Berger’s helicity flux density (1984, J. Fluid Mech., 147, 133) and Pariat’s on the positive and negative polarities, and confirmed that these equations produce different helicity fluxes on the positive and negative polarities. Under the idea of the multiple flux tube model, we propose two interpretations of helicity injection fluxes of twist and writhe; the single flux tube model and the continuous field line model. Recent results of helicity flux injections need to be reanalyzed.
X-Ray and Gamma-Ray Emission of the Shell-Type Supernova Remnant RX J1713.7−3946
Authors: Zhang Li , Yang C. Y.
Published: March 2014

To study possible origins of high-energy gamma-ray emission from shell-type supernova remnants, RX J1713.7$-$3946, we model their nonthermal photon spectra from X-ray to very high energy (VHE) gamma-ray bands in the frame of non-linear diffusive shock acceleration, respectively. In our modeling, the accelerated proton spectrum is calculated based on a semi-analytical solution of the problem of particle acceleration at non-linear shock waves with a free escape boundary at some location upstream, and the accelerated electron spectrum is similar to the proton's spectrum when the electron's momentum is much less than its maximum momentum, which is determined by equating the synchrotron loss time with the acceleration time, and the cutoff shapes are assumed to be an super-exponential. In the one-zone model, we calculated the non-thermal photon spectra of the supernova remnants (SNR) for both leptonic and hadronic cases, and found out that the spectra calculated for both cases can reproduce the observed data by Suzaku, Fermi LAT, and HESS under reasonable model parameters. However, high-energy gamma-ray emission would have a hadronic origin if the observed thickness of the X-ray filament of the SNR is taken into account.
All-Sky Video Orbits of Lyrids 2009
Authors: TÓTh Juraj , Kornoš Leonard , Vereš Peter , ŠIlha Jirí , Kalmancok Dušan , Zigo Pavol , VilÁGi Jozef
Published: March 2014

We report observational results of the Lyrid meteor shower observed by the double-station all-sky video system on the night of 2009 April 21/22 at the Astronomical and Geophysical Observatory of the Comenius University in Modra and Arboretum, Tesárske Mlynany, Slovakia. This observation was the first test of double stations and orbit determination method within the frame of the new Slovak Video Meteor Network (SVMN). We present the whole set of 17 observed orbits of Lyrids as well as the five most precise orbits in detail form. A comparison with the known datasets, precise photographic IAU MDC and SonotaCo video orbits, demonstrate quite good consistency and similar quality.
Suzaku X-Ray Follow-Up Observation of Weak-Lensing-Detected Halos in the Field around ZwCl 0823.2+0425
Authors: Watanabe Eri , Takizawa Motokazu , Nakazawa Kazuhiro , Okabe Nobuhiro , Kawaharada Madoka , Babul Arif , Finoguenov Alexis , Smith Graham P. , Taylor James E.
Published: March 2014

We present the results of a Suzaku X-ray follow-up observation of weak-lensing-detected halos in the field around galaxy cluster ZwCl 0823.2$+$0425. We clearly detected X-ray emission associated with most of these halos, and determined their detailed physical parameters, such as the X-ray luminosity, temperature, and metal abundance, for the first time. We found that the X-ray luminosity–temperature relation for these halos agrees with the former typical results. With the mass determined from the weak gravitational lensing data, the mass–temperature relation for them was also investigated, and was found to be consistent with the prediction from a simple self-similar model and the results of previous studies with both lensing and X-ray data. We would like to emphasize that the self-similar scaling relation of the mass and the temperature is shown here for the first time using a weak-lensing selected sample, whereas previous studies of the mass scaling relation used X-ray-selected samples of clusters. Therefore, our study demonstrates the importance of X-ray follow-up observations of shear-selected clusters, and shows that a joint X-ray and lensing analysis will be crucial for clusters discovered by the forthcoming weak-lensing surveys, such as the one planned with Subaru/Hyper-Suprime-Cam.