bluuebunny/crossref_metadata_2025 huggingface dataset:
Soft and Hard X-Ray Emissions from the Anomalous X-Ray Pulsar 4U 0142+61 Observed with Suzaku
Authors: Enoto Teruaki , Makishima Kazuo , Nakazawa Kazuhiro , Kokubun Motohide , Kawaharada Madoka , Kotoku Jun'ichi , Shibazaki Noriaki
Published: March 2014

The anomalous X-ray pulsar 4U 0142$+$61 was observed with Suzaku on 2007 August 15 for a net exposure of $\sim\ $100 ks, and was detected in a 0.4 to $\sim\ $70 keV energy band. The intrinsic pulse period was determined to be 8.68878$\ \pm\ $0.00005 s, in agreement with an extrapolation from previous measurements. The broadband Suzaku spectra enabled a first simultaneous and accurate measurement of the soft and hard components of this object by a single satellite. The former can be reproduced by two blackbodies, or slightly better by a resonant cyclotron scattering model. The hard component can be approximated by a power-law of photon index of $\Gamma_{\rm h}$  $\sim\ $ 0.9 when the soft component is represented by the resonant cyclotron scattering model, and its high-energy cutoff is constrained as $\gt\ $180 keV. Assuming an isotropic emission at a distance of 3.6 kpc, the unabsorbed 1–10 keV and 10–70 keV luminosities of the soft and hard components were calculated to be 2.8 $\times$ 10$^{35}\ $erg s$^{-1}$ and 6.8 $\times$ 10$^{34}\ $erg s$^{-1}$, respectively. Their sum becomes $\sim\ $10$^3$ times as large as the estimated spin-down luminosity. On a time scale of 30 ks, the hard component exhibited evidence of variations either in its normalization or pulse shape.
Prominent Polarized Flares of the Blazars AO 0235164 and PKS 1510089
Authors: Sasada Mahito , Uemura Makoto , Fukazawa Yasushi , Kawabata Koji S. , Ikejiri Yuki , Itoh Ryosuke , Yamanaka Masayuki , Sakimoto Kiyoshi , Ohsugi Takashi , Yoshida Michitoshi , Sato Shuji , Kino Masaru
Published: March 2014

We report on multi-band photometric and polarimetric observations of the blazars AO 0235$+$164 and PKS 1510$-$089. These two blazars were active in 2008 and 2009, respectively. In these active states, prominent short flares were observed in both objects, having amplitudes of $\gt$1mag within 10d. The $V$$-$$J$ color became bluer when the objects were brighter in these flares. On the other hand, the color of PKS 1510$-$089 exhibited a trend that it became redder when it was brighter, except for its prominent flare. This redder-when-brighter trend can be explained by the strong contribution of thermal emission from an accretion disk. The polarization degree increased at the flares, and reached $\gt$25% at the maxima. We compared these flares in AO 0235$+$164 and PKS 1510$-$089 with other short flares that were detected by our monitoring of 41 blazars. Those two flares had one of the largest variation amplitudes in both flux and polarization degree. Furthermore, we found a significant positive correlation between the amplitudes of the flux and the polarization degree in short flares. It indicates that the short flares originate from the region where the magnetic field is aligned.
Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud
Authors: Machida Masahiro N. , Inutsuka Shu-ichiro , Matsumoto Tomoaki
Published: March 2014

Using resistive magnetohydrodynamics simulation, we consider circumstellar disk formation in a strongly magnetized cloud. As the initial state, an isolated cloud core embedded in a low-density interstellar medium with a uniform magnetic field was adopted. The cloud evolution was calculated until almost all gas inside the initial cloud fell onto either the circumstellar disk or a protostar, and a part of the gas was ejected into the interstellar medium by the protostellar outflow driven by the circumstellar disk. In the early main accretion phase, the disk size is limited to $\sim\ $10 AU because the angular momentum of the circumstellar disk is effectively transferred by both magnetic braking and the protostellar outflow. In the later main accretion phase, however, the circumstellar disk grows rapidly and exceeds $\gtrsim\ $100 AU by the end of the main accretion phase. This rapid growth of the circumstellar disk is caused by depletion of the infalling envelope, while magnetic braking is effective when the infalling envelope is more massive than the circumstellar disk. The infalling envelope cannot brake the circumstellar disk when the latter is more massive than the former. In addition, the protostellar outflow weakens and disappears in the later main accretion phase, because the outflow is powered by gas accretion onto the circumstellar disk. Although the circumstellar disk formed in a magnetized cloud is considerably smaller than that in an unmagnetized cloud, a circumstellar disk exceeding 100 AU can form even in a strongly magnetized cloud.
Properties of Dust and PAHs in the Hot Plasma of the Elliptical Galaxy NGC 4125 Revealed with AKARI and Spitzer Space Telescope
Authors: Kaneda Hidehiro , Ishihara Daisuke , Onaka Takashi , Suzuki Toyoaki , Mori Tatsuya , Oyabu Shinki , Yamagishi Mitsuyoshi
Published: March 2014

We present the spatial distributions of dust and polycyclic aromatic hydrocarbons (PAHs) in the elliptical galaxy NGC 4125, revealed by AKARI and Spitzer. NGC 4125 is relatively bright in dust and PAH emision for elliptical galaxies, although it certainly possesses diffuse interstellar hot plasma, indicated by the high spatial resolution X-ray data of Chandra. We investigate how the dust and PAHs interact with the X-ray plasma or avoid the interaction by comparing their spatial distributions. We find that the distributions of the PAHs and dust are different from each other, both showing a significant deviation from a smooth stellar distribution. The PAH emission predominantly comes from a dust lane, a compact dense molecular gas region in the galactic center, where the PAHs are likely to have been protected from the interaction with the X-ray plasma. The dust emission has more extended structures, similar to the distribution of the X-ray plasma, suggesting their interaction to some extent. We also discuss a possible origin of the dust and PAHs in the galaxy.
Sagittarius A Molecular Cloud Complex in H13CO+ and Thermal SiO Emission Lines
Authors: Tsuboi Masato , Tadaki Ken-ichi , Miyazaki Atsushi , Handa Toshihiro
Published: March 2014

We present results of a high-resolution wide-field mapping observation of the Sagittarius A (Sgr A) molecular cloud complex in H$^{13}$CO$^+$  $J$  $=$ 1–0 and thermal SiO $J$  $=$ 2–1 emission lines with the 25-beam receiver of the 100 GHz band operating on the Nobeyama Radio Observatory 45-m telescope. The mapping area covers a 0$^\circ\!\!\!.$5 $\times$ 0$^\circ\!\!\!.$5 area involving several named molecular clouds, for example GCM$-$0.02$-$0.07, GCM$-$0.13$-$0.08, GCM 0.11$-$0.11, the Sickle molecular cloud, the Arched filaments molecular cloud, and so on. The data have an effective angular resolution of 26$''$. The H$^{13}$CO$^+$ emission line is a famous tracer of molecular gas mass because the line is optically thin, even in the Galactic center region, and is not emphasized by shock. The emission line presents a clumpy distribution of the molecular cloud. The averaged fractional abundance in the Sgr A complex is $N$(H$^{13}$CO$^+$)$/N_{\mathrm{H_2}}$  $\simeq$ (1.8$\ \pm\ $0.4) $\times$ 10$^{-11}$, comparing the LTE mass and the virial theorem mass. The SiO emission line is a famous and reliable tracer of shocked molecular gas. We find many molecular clouds that are remarkable only in the SiO emission line. Such molecular clouds have a large velocity width of up to 60 km s$^{-1}$. The brightness temperature ratio is up to $T_{\mathrm{B}}$(SiO)$/T_{\mathrm{B}}$(H$^{13}$CO$^+$) $\lesssim$ 8. The features are dominated by shock SiO-enriched gas. In such clouds, the ratio of the fractional abundance of SiO and H$^{13}$CO$^+$ molecules is $X$(SiO)$/X$(H$^{13}$CO$^+$) $\sim$ 100. The features are presumably made by supernova remnants. We found a prototypical example in GCM$-$0.02$-$0.07. It has two distinct structures. One is a ridge-like structure contacting with the Sgr A East shell; another is an expanding shell-like structure. There is a wide-velocity width ridge of SiO-enriched gas in GCM 0.11$-$0.11, which is adjacent to Vertical filaments. This suggests that the collision with the molecular cloud accelerates relativistic electrons, which illuminate the Vertical filaments–Polarized Plumes complex.
Accuracy Diagrams for the Galactic Rotation Curve and Kinematical Distances
Authors: Sofue Yoshiaki
Published: March 2014

We revisit methods used to determine the Galactic rotation curve and kinematical distances from radial velocities and proper motions. We construct ``accuracy diagrams'' to show the distributions in the galactic plane of expected uncertainties in the derived quantities, such as rotation velocities and kinematical distances. We discuss how to optimize the source selection for measurements of kinematical quantities based on accuracy diagrams.
Near-Solar-Circle Method for Determining the Galactic Constants
Authors: Sofue Yoshiaki , Nagayama Takumi , Matsui Makoto , Nakagawa Akiharu
Published: March 2014

We propose a method to determine the galactic constants, $R_0$ (distance to the Galactic Center) and $V_0$ (rotation velocity of the Sun), from measurements of the distances, radial velocities and proper motions of objects near the solar circle. This is a modification of the solar-circle method to a more practical observational method. We applied the method to determine $R_0$ using data from the literature with known distances and radial velocities, and obtained $R_0$$=$ 7.54$\ \pm\ $0.77 kpc.
Spectral Evolution of the Unusual Slow Nova V5558 Sagittarii
Authors: Tanaka Jumpei , Nogami Daisaku , Fujii Mitsugu , Ayani Kazuya , Kato Taichi , Maehara Hiroyuki , Kiyota Seiichiro , Nakajima Kazuhiro
Published: March 2014

We report on the spectral evolution of the enigmatic, very slow nova V5558 Sgr, based on low-resolution spectra obtained at the Fujii-Bisei Observatory and the Bisei Astronomical Observatory, Japan during the period of 2007 April 6 to 2008 May 3. V5558 Sgr shows a pre-maximum halt, and then several flare-like rebrightenings, which is similar to another very slow nova, V723 Cas. In our observations, the spectral type of V5558 Sgr evolved from the He/N type toward the Fe II type during a pre-maximum halt, and then toward the He/N type again. This course of spectral transition was observed for the first time in the long history of nova research. In the rebrightening stage after the initial brightness maximum, we could identify many emission lines accompanied by a stronger absorption component of the P Cyg profile at the brightness maxima. We found that the velocity of the P Cyg absorption component, measured from the emission peak, decreased at the brightness maxima. Furthermore, we compared the spectra of V5558 Sgr with V723 Cas, and other novae that exhibited several rebrightenings during the early phase.
Skewed Distributions and Opposite Velocity Gradients of Submillimeter Molecular Lines in Low-Mass Protostellar Envelopes
Authors: Takakuwa Shigehisa , Kamazaki Takeshi
Published: March 2014

We have made mapping observations of L 1551 IRS 5, L 1551 NE, L 723, and L 43 and single-point observations of IRAS 16293$-$2422 in the submillimeter CS ($J$  $=$ 7–6) and HCN ($J$  $=$ 4–3) lines with Atacama Submillimeter Telescope Experiment (ASTE). Using the present data and our previous ASTE observations of L 483 and B 335 together, we found a definite correlation between source bolometric luminosities and total integrated intensities of the submillimeter lines ($I_{\rm CS}$  $\propto$  $L_{\rm bol}^{0.92}$). The combined ASTE $+$ Submillimeter Array CS (7–6) image of L 1551 IRS 5 exhibits an extended ($\sim$ 2000 AU) component tracing the associated reflection nebula at west and southwest, as well as a compact ($\lesssim$ 500 AU) component centered on the protostellar position. The peaks of the CS and HCN emissions in L 1551 NE are not located at the protostellar position but offset ($\sim$ 1400 AU) toward the associated reflection nebula at west. By statistical analyses, we confirmed the velocity gradients of the CS (7–6) emission that are opposite to those of the millimeter lines along the outflow direction, which we reported in our early paper. The magnitudes of the submillimeter velocity gradients are estimated to be (9.7$\ \pm\ $1.7) $\times$ 10$^{-3}\ $km s$^{-1}\ $arcsec$^{-1}\ $ in L 1551 IRS 5 and (7.6$\ \pm\ $2.4) $\times$ 10$^{-3}\ $km s$^{-1}\ $arcsec$^{-1}\ $ in L 483. We suggest that the “skewed” submillimeter molecular emissions toward the associated reflection nebulae at a few thousand AU scale trace the warm ($\gtrsim$ 40 K) walls of the envelope cavities, excavated by the associated outflows and directly irradiated by the central protostars. The opposite velocity gradients along the outflow direction likely reflect the dispersing gas motion at the wall of the cavity in envelopes perpendicular to the outflow.
Stellar Parameters and Chemical Abundances of G Giants
Authors: Wang Liang , Liu Yujuan , Zhao Gang , Sato Bun'ei
Published: March 2014

We present basic stellar parameters of 99 late-type G giants based on high-resolution spectra obtained by the High Dispersion Spectrograph attached to Subaru Telescope. These stars are targets of a Doppler survey program searching for extra-solar planets among evolved stars, with a metallicity of $-$0.8 $\lt$ [Fe$/$H] $\lt$  $+$0.2. We also derived their abundances of 15 chemical elements, including four $\alpha $-elements (Mg, Si, Ca, Ti), three odd-Z light elements (Al, K, Sc), four iron peak elements (V, Cr, Fe, Ni), and four neutron-capture elements (Y, Ba, La, Eu). Kinematic properties reveal that most of the program stars belong to the thin disk.
Oscillation Phenomena in the Disk around the Massive Black Hole Sagittarius A*
Authors: Miyoshi Makoto , Shen Zhi-Qiang , Oyama Tomoaki , Takahashi Rohta , Kato Yoshiaki
Published: March 2014

We report the detection of radio QPOs with structure changes using the Very Long Baseline Array (VLBA) at 43 GHz. We found conspicuous patterned changes of the structure with $P$  $=$ 16.8$\ \pm\ $1.4, 22.2$\ \pm\ $1.4, 31.4$\ \pm\ $1.5, 56.4$\ \pm\ $6 min roughly in a 3:4:6:10 ratio. The first two periods show a rotating one-arm structure, while $P$  $=$ 31.4 min shows a rotating 3-arm structure, as if viewed edge-on. At the central 50$\ \mu$as the $P$  $=$ 56.4 min period shows a double-amplitude variation of those in its surroundings. The spatial distributions of the oscillation periods suggest that the disk of Sgr A$^{*}$ is roughly edge-on, rotating around an axis with $PA$  $=$  $-$10$^{\circ}$. Presumably, the observed VLBI images of Sgr A$^{*}$ at 43 GHz retain several features of the black hole accretion disk of Sgr A$^{*}$ in spite of being obscured and broadened by scattering of surrounding plasma.
Correlation between Interstellar Polarization and Dust Temperature: Is the Alignment of Grains by Radiative Torques Ubiquitous?
Authors: Matsumura Masafumi , Kameura Youko , Kawabata Koji S. , Akitaya Hiroshi , Isogai Mizuki , Seki Munezo
Published: March 2014

We have investigated the efficiency of interstellar polarization, $p_\lambda/A_\lambda$, where $p_\lambda$ is the fractional linear polarization and $A_\lambda$ is the extinction, in 14 lines of sight as a function of the wavelength, $\lambda$. We used the data of lines of sight to the Pleiades cluster obtained with the low-dispersion spectropolarimeter HBS as well as those in literature. It has been found that the polarization efficiency, $p_\lambda/A_\lambda$, is proportional to exp ($-\beta/\lambda$) in wavelength, $\lambda$  $\approx$ 0.4–0.8$\ \mu$m, where $\beta$ is a parameter that varies from 0.5 to 1.2$\ \mu$m. We find that $\beta$ is negatively correlated with the dust temperature deduced from infrared data by Schlegel et al. (1998, ApJ, 500, 525), suggesting that the polarization efficiency is higher in short wavelengths for higher temperature. According to the alignment theory by radiative torques (RATs), if the radiation is stronger, RATs will make small grains align better, and the polarization efficiency will increase at short wavelengths. Our finding of the correlation between $\beta$ and the temperature is consistent with what is expected with the alignment mechanism by RATs.
AKARI/IRC Broadband Mid-Infrared Data as an Indicator of the Star-Formation Rate
Authors: Yuan Fang-Ting , Takeuchi Tsutomu T. , Buat Véronique , Heinis Sébastien , Giovannoli Elodie , Murata Katsuhiro L. , Iglesias-PÁRamo Jorge , Burgarella Denis
Published: March 2014

AKARI/Infrared Camera (IRC) Point Source Catalog provides a large amount of flux data at S9W (9$\ \mu$m) and L18W (18$\ \mu$m) bands. With the goal of constructing Star-Formation Rate (SFR) calculations using IRC data, we analyzed an IR selected GALEX-SDSS-2MASS-AKARI(IRC/Far-Infrared Surveyor) sample of 153 nearby galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to correct an underestimation for extended sources raised by the point-spread function photometry. SFRs of these galaxies were derived by the spectral energy distribution fitting program CIGALE. In spite of complicated features contained in these bands, both the S9W and L18W emission correlate with the SFR of galaxies. The SFR calibrations using S9W and L18W are presented for the first time. These calibrations agree well with previous works based on Spitzer data within the scatters, and should be applicable to dust-rich galaxies.
Rotating Black Holes as Central Engines of Long Gamma-Ray Bursts: Faster is Better
Authors: Nagataki Shigehiro
Published: March 2014

We performed simulations of collapsars with different Kerr parameters of $a$  $=$ 0, 0.5, 0.9, and 0.95. It was shown that a more rapidly rotating black hole is driving a more energetic jet. No jet is seen for the case of the Schwartzschild black-hole case, while the total energy of the jet is as large as 10$^{50}\ $erg for a rapidly rotating Kerr black-hole case ($a$  $=$ 0.95). In order to explain the high luminosity of a gamma-ray burst, it is concluded that a rapidly rotating black hole is favored ('faster is better'). We also find that in the case of $a$  $=$ 0.95, (i) a stagnation region is clearly found in the jet region, (ii) ordered poloidal field lines are seen in the jet, (iii) the jet region is surrounded by a 'wall-like' structure that has a higher pressure than the jet region, and contains strong vertical magnetic fields, and (iv) the jet is initiated by an outgoing Poynting flux from the outer horizon of the black hole (Blandford–Znajek effect). The bulk Lorentz factor of the jet is still on the order of unity. However, the energy density of electro-magnetic fields is dominated by the one of rest-mass in the jet. It can be expected that a relativistic jet will be seen if we perform a simulation for a longer time scale (of the order of 10–100 s).
Center-to-Limb Variation of Radio Emissions from Thermal-Rich and Thermal-Poor Solar Flares
Authors: Kawate Tomoko , Asai Ayumi , Ichimoto Kiyoshi
Published: March 2014

A statistical analysis of radio flare events was conducted by using the event list of Nobeyama Radioheliograph in the years 1996–2009. We examined center-to-limb variations of 17 GHz and 34 GHz fluxes by dividing the flare events into different groups according to the ``thermal plasma richness'' (ratio of the peak flux of soft X-ray to nonthermal radio emissions) and the duration of radio bursts. It was found that the peak flux at 17 and 34 GHz tended to be higher toward the limb for thermal-rich flares with short durations. We propose that the thermal-rich flares, which are supposed to be associated with an efficient precipitation of high-energy particles into the chromosphere, have a pitch-angle distribution of nonthermal electrons with a higher population along the flare loop.
Radio Imaging of the NGC 1333 IRAS 4A Region: Envelope, Disks, and Outflows of a Protostellar Binary System
Authors: Choi Minho , Kang Miju , Tatematsu Ken'ichi , Lee Jeong-Eun , Park Geumsook
Published: March 2014

The NGC 1333 IRAS 4A protobinary was observed in the 1.3 cm and 6.9 mm continuum and the ammonia and SiO lines, with an angular resolution of $\sim$ 0$''\!\!\!.$4. The continuum maps show the circumstellar structures of two protostars, A1 and A2. The A1 system is brighter and more massive than the A2 system. The ratio of mass, including dense gas and the protostar, is $\sim$ 6. The properties of the circumstellar disks and outflows suggest that A1 may be younger than A2. The deflected part of the northeastern jet of A2 is bright in the SiO line, and the distance between the brightest peak and the deflection point suggests that the enhancement of SiO takes $\sim$ 100 yr after a collision with a dense core. Ammonia maps show a small structure that seems to be a part of the obstructing core. The outflow properties were studied by comparing interferometric maps of the SiO, ammonia, formaldehyde, and HCN lines. Their overall structures agree well, suggesting that these species are excited by the same mechanism. However, the intensity distributions show that SiO is chemically unique. SiO may be directly linked to the primary jet, while the other species may be tracing the entrained ambient gas.
Fast Automatic Redshift Determination Using Absorption Lines Recognition
Authors: Han Jin-Shu , Luo A-Li , Zhao Yong-Heng
Published: March 2014

To precisely measure the redshifts of non-ELGs (ELGs: emission-line galaxies), weaker-ELGs and galaxies with only one emission line that is clearly visible in the optical band, a fast automatic redshift determination algorithm (FRA) is proposed, which is different from the widely used cross-correlation method. The algorithm has higher speed because it determines the redshift by extracting and recognizing two pairs of prominent absorption lines in the blue band of a spectrum, G-band $\lambda$4306 and H${\gamma}$$\lambda$4342 (vacuum wavelength), H${\beta}$$\lambda$4863 and Mg $\lambda$5177, rather than through matching an observational galaxy spectrum with the complete galaxy templates. Moreover, a wide range of redshift measurements from 0 to 0.65 and relatively high success rates can be reached by FRA. For spectra with a relatively wide wavelength range and with a resolution above $R$$=$ 1000, FRA is an efficient automatic algorithm that can be used in spectra redshift surveys with large amounts of data.
XO-2b: a Prograde Planet with Negligible Eccentricity and an Additional Radial Velocity Variation
Authors: Narita Norio , Hirano Teruyuki , Sato Bun'ei , Harakawa Hiroki , Fukui Akihiko , Aoki Wako , Tamura Motohide
Published: March 2014

We present precise radial velocities of XO-2 taken with the Subaru HDS, covering two transits of XO-2b with an interval of nearly two years. The data suggest that the orbital eccentricity of XO-2b is consistent with zero within 2$\ \sigma$ ($e$$=$ 0.045$\ \pm\ $0.024), and that the orbit of XO-2b is prograde (the sky-projected spin–orbit alignment angle $\lambda$$=$ 10$^{\circ}\ \pm\ $72$^{\circ}$). The poor constraint of $\lambda$ is due to a small impact parameter (the orbital inclination of XO-2b is almost 90$^{\circ}$). The data also provide an improved estimate of the mass of XO-2b as 0.62$\ \pm\ $0.02$\ M_{\rm Jup}$. Further, we find a long-term radial velocity variation in this system. Additional radial velocity measurements are necessary to specify the cause of this additional variation.
Atlas and Catalog of Dark Clouds Based on the 2 Micron All Sky Survey
Authors: Dobashi Kazuhito
Published: March 2014

This paper presents an atlas and catalog of dark clouds derived based on the 2 Micron All Sky Survey Point Source Catalog (2MASS PSC). Color excess maps of $E$($J-H$) and $E$($H-K_{\rm S}$) as well as extinction maps of $A_J$, $A_H$, and $A_{K_{\rm S}}$ covering all of the sky have been produced at the 1$'$ grid with a changing angular resolution ($\sim\ $1$'$–12$'$), depending on the regions in the sky. Maps drawn at the lower 15$'$ grid with a fixed 1$^\circ$ resolution were also derived for various sets of threshold magnitudes in the $J$, $H$, and $K_{\rm S}$ bands to estimate the background star colors and star densities needed to derive the color excess and extinction maps. The maps obtained in this work are presented on various scales in a series of figures that can be used as an atlas of dark clouds for general research purposes. On the basis of the $E$($J-H$) and $A_J$ maps drawn at the 1$'$ grid, we have carried out a systematic survey for dark clouds all over the sky. In total, we identified 7614 dark clouds, and measured the coordinates, extents, and $A_V$ values for each of them. We also searched for their counterparts in a previously published catalog of dark clouds based on the optical photographic plates DSS (Dobashi et al. 2005, PASJ, 57, S1). These cloud parameters, including the information of the counterparts, are compiled into a new catalog of dark clouds. The atlas and catalog organized in this paper mainly trace relatively dense regions in dark clouds, revealing a number of dense cloud cores leading to star formation, while those presented by Dobashi et al. (2005) based on the optical database are more suited to trace less-dense regions and to reveal the global extents of dark clouds. These two datasets are complementary, and all together, they are useful to picture the structures of dark clouds in various density ranges.
In-Orbit Performance of MAXI Gas Slit Camera (GSC) on ISS
Authors: Sugizaki Mutsumi , Mihara Tatehiro , Serino Motoko , Yamamoto Takayuki , Matsuoka Masaru , Kohama Mitsuhiro , Tomida Hiroshi , Ueno Shiro , Kawai Nobuyuki , Morii Mikio , Sugimori Kousuke , Nakahira Satoshi , Yamaoka Kazutaka , Yoshida Atsumasa , Nakajima Motoki , Negoro Hitoshi , Eguchi Satoshi , Isobe Naoki , Ueda Yoshihiro , Tsunemi Hiroshi
Published: March 2014

We report on the in-orbit performance of the Gas Slit Camera (GSC) on the MAXI (Monitor of All-sky X-ray Image) mission carried on the International Space Station (ISS). Its commissioning operation, which started on 2009 August 8, confirmed the basic performances of the effective area in the energy band of 2–30 keV, the spatial resolution of the slit-and-slat collimator and detector with 1 $^\circ\!\!\!.$ 5 FWHM, the source visibility of 40–150 seconds for each scan cycle, and the sky coverage of 85% per 92-minute orbital period and 95% per day. The gas gains and read-out amplifier gains have been stable within 1%. The background rate is consistent with the past X-ray experiments operated at a similar low-earth orbit if its relation with the geomagnetic cutoff rigidity is extrapolated to high latitude. We also present the status of the in-orbit operation and a calibration of the effective area and the energy response matrix using Crab-nebula data.
The First MAXI/GSC Catalog in the High Galactic-Latitude Sky
Authors: Hiroi Kazuo , Ueda Yoshihiro , Isobe Naoki , Hayashida Masaaki , Eguchi Satoshi , Sugizaki Mutsumi , Kawai Nobuyuki , Tsunemi Hiroshi , Matsuoka Masaru , Mihara Tatehiro , Yamaoka Kazutaka , Ishikawa Masaki , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Morii Mikio , Nakagawa Yujin E. , Nakahira Satoshi , Nakajima Motoki , Negoro Hitoshi , Serino Motoko , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Toizumi Takahiro , Tomida Hiroshi , Tsuboi Yohko , Ueno Shiro , Usui Ryuichi , Yamamoto Takayuki , Yamazaki Kyohei , Yoshida Atsumasa
Published: March 2014

We present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission at high Galactic latitudes ( $\vert b\vert$$>$ 10 $^{\circ}$ ), produced from the first 7-month data (2009 September 1 to 2010 March 31) of the Gas Slit Camera in the 4–10 keV band. We have developed an analysis procedure to detect faint sources from the MAXI data, utilizing a maximum likelihood image fitting method, where the image response, background, and detailed observational conditions are taken into account. The catalog consists of 143 X-ray sources above the 7 $\sigma$ significance level with a limiting sensitivity of $\sim\ $ 1.5 $\times$ 10 $^{-11}\ $ erg cm $^{-2}\ $ s $^{-1}$ (1.2 mCrab) in the 4–10 keV band. Among them, we have identified 38 Galactic/LMC/SMC objects, 48 galaxy clusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Four other sources are confused with multiple objects, and one remains unidentified. The log $\ N$ –log $\ S$ relation of extragalactic objects is in good agreement with the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantly changed since that produced 30 yr ago.
A Large X-Ray Flare from a Single Weak-Lined T Tauri Star TWA-7 Detected with MAXI GSC
Authors: Uzawa Akiko , Tsuboi Yohko , Morii Mikio , Yamazaki Kyohei , Kawai Nobuyuki , Matsuoka Masaru , Nakahira Satoshi , Serino Motoko , Matsumura Takanori , Mihara Tatehiro , Tomida Hiroshi , Ueda Yoshihiro , Sugizaki Mutsumi , Ueno Shiro , Daikyuji Arata , Ebisawa Ken , Eguchi Satoshi , Hiroi Kazuo , Ishikawa Masaki , Isobe Naoki , Kawasaki Kazuyoshi , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Kotani Taro , Nakagawa Yujin E. , Nakajima Motoki , Negoro Hitoshi , Ozawa Hiroshi , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Tsunemi Hiroshi , Usui Ryuichi , Yamamoto Takayuki , Yamaoka Kazutaka , Yoshida Atsumasa
Published: March 2014

We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of 3 $\times$ 10 $^{-9}\ $ erg cm $^{-2}\ $ s $^{-1}$ in 2–20 keV band during the scan transit starting at 2010-09-07 18:24:30 (UT). The estimated X-ray luminosity at the scan in the energy band is 3 $\times$ 10 $^{32}\ $ erg s $^{-1}$ , indicating that the event is among the largest X-ray flares from T Tauri stars. Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log $\ L_{\rm X}/L_{\rm bol}$$=$$-$ 0.1 $^{+0.2}_{-0.3}$ ; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to generate such big flares in T Tauri stars.
Suzaku Observation of the Intermediate Polar V1223 Sagittarii
Authors: Hayashi Takayuki , Ishida Manabu , Terada Yukikatsu , Bamba Aya , Shionome Takeshi
Published: March 2014

We report on the Suzaku observation of the intermediate polar V1223 Sagittarii. Using a multi-temperature plasma emission model with its reflection from a cold matter, we obtained the shock temperature to be 37.9 $^{+5.1}_{-4.6}\ $ keV. This constrains the mass and the radius of the white dwarf (WD) in the ranges 0.82 $^{+0.05}_{-0.06}\ M_\odot$ and (6.9 $\ \pm\ $ 0.4) $\times$ 10 $^{8}\ $ cm, respectively, with the aid of a WD mass–radius relation. The solid angle of the reflector viewed from the post-shock plasma was measured to be $\Omega/$ 2 $\pi$$=$ 0.91 $\ \pm\ $ 0.26. A fluorescent iron K $\alpha $ emission line was detected, whose central energy was discovered to be modulated with the WD rotation for the first time in magnetic-CVs. Detailed spectral analysis indicates that the line comprises a stable 6.4 keV component and a red-shifted component, the latter of which appears only around the rotational intensity-minimum phase. The equivalent width ( $EW$ ) of the former stable component, $\sim\ $ 80 eV, together with the measured $\Omega$ indicates that the major reflector is the WD surface, and the shock height is not more than 7% of the WD radius. Comparing this limitation to the height predicted by the Aizu model (Aizu, 1973, Prog. Theor. Phys., 50, 344), we estimated the fractional area onto which the accretion occurs to be $<\ $ 7 $\times$ 10 $^{-3}$ of the WD radius, which is the most severe constraint in non-eclipsing IPs. The red-shifted iron line component, on the other hand, can be interpreted as emanating from the pre-shock accretion flow via fluorescence. Its $EW$ (28 $^{+44}_{-13}\ $ eV) and the central energy (6.30 $_{-0.05}^{+0.07}\ $ keV) at the intensity-minimum phase are consistent with this interpretation.
Near-Infrared and X-Ray Observations of XSS J12270−4859
Authors: Saitou Kei , Tsujimoto Masahiro , Ebisawa Ken , Ishida Manabu , Mukai Koji , Nagayama Takahiro , Nishiyama Shogo , Gandhi Poshak
Published: March 2014

XSS J12270 $-$ 4859 (J12270) is an enigmatic source of unknown nature. Previous studies revealed that the source has unusual X-ray temporal characteristics, including repetitive short-term flares, followed by spectral hardening, non-periodic dips, and dichotomy in activity; i.e., intervals filled with flares and those without. Together with a power-law X-ray spectrum, it is suggested to be a low-mass X-ray binary. In order to better understand the object, we present the results of our near-infrared (NIR) photometry and linear polarimetry observations as well as X-ray spectroscopy observations, which overlap with each other partially in time, taken respectively with the InfraRed Survey Facility (IRSF) and the Rossi X-ray Timing Explorer (RXTE). We detected several simultaneous NIR and X-ray flares for the first time. No significant NIR polarization was obtained. We assembled data taken with IRSF, RXTE, Suzaku, Swift, and other missions in the literature and compared the flare profile and the spectral energy distribution (SED) with some representative high-energy sources. Based on some similarities of the repetitive NIR and X-ray flaring characteristics and the broad SED, we argue that J12270 is reminiscent of microquasars with a synchrotron jet, which is at a very low-luminosity state of $\approx$ 10 $^{-4}$ Eddington luminosity for a stellar mass black hole or neutron star at a reference distance of 1 kpc.
Spectral and Timing Studies of Cyg X-1 in the Low/Hard State with Suzaku
Authors: Torii Shunsuke , Yamada Shin’ya , Makishima Kazuo , Sakurai Soki , Nakazawa Kazuhiro , Noda Hirofumi , Done Chris , Takahashi Hiromitsu , Gandhi Poshak
Published: March 2014

From 2005 to 2009, 25 observations of Cyg X-1 were performed with Suzaku, achieving a total exposure of 446 ks. In all observations, the source was found in the low/hard state, while the 1.5–12.0 keV count rate of the All-Sky Monitor onboard RXTE varied by a factor of $\sim\ $ 3. In each observation, the 10–60 keV HXD-PIN spectrum and the 60–400 keV HXD-GSO spectrum were fitted successfully by a thermal Comptonization model plus reflection by a thick neutral material. As the soft X-ray intensity increased, the Compton $y$ -parameter was found to decrease from 1.0 to 0.6, while the solid angle of reflection increased by $\sim\ $ 30%. Also conducted was a timing analysis over a frequency range of 10 $^{-3}$ –10 Hz. As the source became brighter in soft X-rays, the characteristic frequency of the hard X-ray variation increased from 0.03 to 0.3 Hz, while the fractional hard X-ray variation integrated over 10 $^{-3}$ –10 $^{-2}$ Hz decreased by a factor of $\sim\ $ 5. The signals in the 60–200 keV band were generally found to vary on shorter time scales than those in the 10–60 keV band. These spectral and timing results can be consistently interpreted by presuming that increases in the mass accretion rate cause the Comptonizing hot corona to shrink, while the optically-thick disk to intrude deeper therein.
Suzaku Discovery of Twin Thermal Plasma from the Tornado Nebula
Authors: Sawada Makoto , Go Tsuru Takeshi , Koyama Katsuji , Oka Tomoharu
Published: March 2014

The Tornado nebula (G357.7 $-$ 0.1) is a mysterious radio source with a bright “head” and faint “tail” located in the direction of the Galactic center (GC) region. We here report on the discovery of two diffuse X-ray sources at the head and tail of Tornado with the Suzaku satellite. We found emission lines from highly ionized atoms in the two sources. The spectra have been reproduced by an optically thin thermal plasma with a common temperature of 0.6–0.7 keV. The interstellar absorption ( $N_{\rm H}$ ) of these sources are the same, and are slightly larger than that of the GC distance. Since the estimated distance using the $N_{\rm H}$ value is consistent with radio observations of Tornado, these X-ray sources are likely to be associated with the Tornado nebula. The twin-plasma morphology at both ends of Tornado suggests that the system is a bipolar/outflow source.
Suzaku Observation of the Unidentified Very High Energy Gamma-Ray Source HESS J1702−420
Authors: Fujinaga Takahisa , Bamba Aya , Dotani Tadayasu , Ozaki Masanobu , PÜhlhofer Gerd , Wagner Stefan , Reimer Olaf , Funk Stefan , Hinton Jim
Published: March 2014

A deep X-ray observation of the unidentified very high energy (VHE) gamma-ray source HESS J1702 $-$ 420, for the first time, was carried out by Suzaku. No bright sources were detected in the XIS field of view (FOV), except for two faint point-like sources. The two sources, however, are considered not to be related to HESS J1702 $-$ 420, because their fluxes in the 2–10 keV band ( $\sim\ $ 10 $^{-14}\ $ erg s $^{-1}\ $ cm $^{-2}$ ) are $\sim\ $ 3 orders of magnitude smaller than the VHE gamma-ray flux in the 1–10 TeV band ( $F_{\rm TeV}$$=$ 3.1 $\times$ 10 $^{-11}\ $ erg s $^{-1}\ $ cm $^{-2}$ ). We compared the energy spectrum of diffuse emission, extracted from the entire XIS FOV with those from nearby observations. If we consider the systematic error of background subtraction, no significant diffuse emission was detected with an upper limit of $F_{\rm X}$$<$ 2.7 $\times$ 10 $^{-12}\ $ erg s $^{-1}\ $ cm $^{-2}$ in the 2–10 keV band for an assumed power-law spectrum of $\Gamma$$=$ 2.1 and a source size same as that in the VHE band. The upper limit of the X-ray flux is twelve-times as small as the VHE gamma-ray flux. The large flux ratio ( $F_{\rm TeV}/F_{\rm X}$ ) indicates that HESS J1702 $-$ 420 is another example of a “dark” particle accelerator. If we use a simple one-zone leptonic model, in which VHE gamma-rays are produced through inverse Compton scattering of the cosmic microwave background and interstellar far-infrared emission, and the X-rays via the synchrotron mechanism, an upper limit of the magnetic field (1.7 $\ \mu$ G) is obtained from the flux ratio. Because the magnetic field is weaker than the typical value in the galactic plane (3–10 $\ \mu$ G), the simple one-zone model may not work for HESS J1702 $-$ 420 and a significant fraction of the VHE gamma-rays may originate from protons.
Global Distribution of Fe Kα Lines in the Galactic Center Region Observed with the Suzaku Satellite
Authors: Uchiyama Hideki , Nobukawa Masayoshi , Tsuru Takeshi Go , Koyama Katsuji , Matsumoto Hironori
Published: March 2014

We surveyed spatial profiles of the Fe K $\alpha $ lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We resolved Fe K $\alpha $ line complex into three lines of Fe I, Fe XXV, and Fe XXVI K $\alpha $ , and obtained their spatial intensity profiles with a resolution of $\sim\ $ 0 $^\circ\!\!\!.$ 1. We compared the Fe XXV K $\alpha $ profile with a stellar mass distribution (SMD) model made from near infrared observations. The intensity profile of Fe XXV K $\alpha $ was nicely fitted with the SMD model in the GRXE region, while that in the GCDX region showed a 3.8 $\ \pm\ $ 0.3 (0 $^\circ\!\!\!.$ 2 $<$$\vert l\vert$$<$ 1 $^\circ\!\!\!.$ 5) or 19 $\ \pm\ $ 6 ( $\vert l\vert$$<$ 0 $^\circ\!\!\!.$ 2) times excess over the best-fit SMD model in the GRXE region. Thus, Fe XXV K $\alpha $ in the GCDX is hardly explained by the same origin of the GRXE. In the case of a point-source origin, a new population with the extremely strong Fe XXV K $\alpha $ line is required. An alternative possibility is that the majority of the GCDX is truly diffuse optically thin thermal plasma.
Suzaku Studies of Wide-Band Spectral Variability of the Bright Type I Seyfert Galaxy Markarian 509
Authors: Noda Hirofumi , Makishima Kazuo , Yamada Shin’ya , Torii Shunsuke , Sakurai Soki , Nakazawa Kazuhiro
Published: March 2014

The Type I Seyfert galaxy Markarian 509 was observed with Suzaku in 2010 November, for a gross time span of 2.2 days. The timing and spectral properties of the 0.5–45 keV X-rays, detected with the XIS and HXD, consistently revealed the presence of a soft spectral component that remained constant while the total X-ray intensity varied by $\pm$ 10%. This stable soft component, found in the 0.5–3.0 keV range, was interpreted as being a result of thermal Comptonization in a corona with a temperature of $\sim\ $ 0.5 keV and an optical depth of $\sim\ $ 18. The time-avearged 0.5–45 keV Suzaku spectrum was reproduced successfully, as a combination of this thermal Comptonization component, a harder power-law of photon index $\sim\ $ 1.8, moderate reflection, and an iron K-emission line. By analyzing four archival Suzaku datasets of the same object obtained in 2006, the thermal Comptonization component, which was stable during 2.2-day pointing in 2010, was found to vary on time scales of a few weeks, independently of the power-law component. Implications of these results are discussed in terms of a “multi-zone Comptonization” view, obtained with Suzaku from the black-hole binary Cygnus X-1.
Revisit of Local X-Ray Luminosity Function of Active Galactic Nuclei with the MAXI Extragalactic Survey
Authors: Ueda Yoshihiro , Hiroi Kazuo , Isobe Naoki , Hayashida Masaaki , Eguchi Satoshi , Sugizaki Mutsumi , Kawai Nobuyuki , Tsunemi Hiroshi , Mihara Tatehiro , Matsuoka Masaru , Ishikawa Masaki , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Morii Mikio , Nakagawa Yujin E. , Nakahira Satoshi , Nakajima Motoki , Negoro Hitoshi , Serino Motoko , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Toizumi Takahiro , Tomida Hiroshi , Tsuboi Yohko , Ueno Shiro , Usui Ryuichi , Yamamoto Takayuki , Yamaoka Kazutaka , Yamazaki Kyohei , Yoshida Atsumasa
Published: March 2014

We constructed a new X-ray (2–10 keV) luminosity function of Compton-thin active galactic nuclei (AGNs) in the local universe, using the first MAXI/GSC source catalog surveyed in the 4–10 keV band. The sample consists of 37 non-blazar AGNs at $z$$=$ 0.002–0.2, whose identification is highly ( $>\ $ 97%) complete. We confirmed the trend that the fraction of absorbed AGNs with $N_{\rm H}$$>\ $ 10 $^{22}$ cm $^{-2}$ rapidly decreases against the luminosity ( $L_{\rm X}$ ), from 0.73 $\ \pm\ $ 0.10 at $L_{\rm X}$$=$ 10 $^{42-43.5}$ erg s $^{-1}$ to 0.12 $\ \pm\ $ 0.08 at $L_{\rm X}$$=$ 10 $^{43.5-45.5}$ erg s $^{-1}$ . The obtained luminosity function was well-fitted with a smoothly connected double power-law model whose indices are $\gamma_1$$=$ 0.84 (fixed) and $\gamma_2$$=$ 2.0 $\ \pm\ $ 0.2 below and above the break luminosity, $L_{*}$$=$ 10 $^{43.3\pm0.4}$ erg s $^{-1}$ , respectively. While the result of the MAXI/GSC agrees well with that of HEAO-1 at $L_{\rm X}$$\gtrsim$ 10 $^{43.5}$ erg s $^{-1}$ , it gives a larger number density at the lower luminosity range. A comparison between our luminosity function in the 2–10 keV band and that in the 14–195 keV band obtained from the Swift/BAT survey indicates that the averaged broad-band spectra in the 2–200 keV band should depend on the luminosity, approximated by $\Gamma$$\sim$ 1.7 for $L_{\rm X}$$\lesssim$ 10 $^{44}$ erg s $^{-1}$ , while $\Gamma$$\sim$ 2.0 for $L_{\rm X}$$\gtrsim$ 10 $^{44}$ erg s $^{-1}$ . This trend was confirmed by the correlation between the luminosities in the 2–10 keV and 14–195 keV bands in our sample. We argue that there is no contradiction in the luminosity functions between above and below 10 keV once this effect is taken into account.
Suzaku Observations of Metal Distributions in the Intracluster Medium of the Centaurus Cluster
Authors: Sakuma Eri , Ota Naomi , Sato Kosuke , Sato Takuya , Matsushita Kyoko
Published: March 2014

We report the first observations of metal distributions in the intracluster medium of the Centaurus cluster up to $\sim\ $ 0.17 $\ r_{180}$ with Suzaku. Radial profiles of the O, Mg, Si, S, Ar, Ca, and Fe were determined at the outer region of the cluster, and their variations appear to be similar to each other. Within the cool core region ( $r$  $<$ 0.045 $\ r_{180}$ ), all of the metal distributions sharply increased toward the center. In the central region ( $r$  $<$ 0.015 $\ r_{180}$ ), the abundances of Si, S, Ar, Ca, and Fe were 1.5–1.8 solar, while those of O and Mg were approximately 1 solar. The derived abundance ratios of O and Mg to Fe were slightly lower than those of a set of other clusters. In contrast, the calculated mass-to-light ratios (MLRs) for O, Mg, and Fe were larger than those of the other clusters. For the outer region of the cool core ( $r$  $>$ 0.07 $\ r_{180}$ ), all of the abundances were almost constant at 0.5 solar. The derived MLRs were comparable to those of the other clusters. This suggests that the cD galaxy of the Centaurus cluster efficiently supplies more Fe than the other clusters.
Suzaku Observation of Nearby On-Going Merger Cluster Abell 3627
Authors: Nishino Sho , Fukazawa Yasushi , Hayashi Katsuhiro
Published: March 2014

We present the results of the Suzaku observation of a nearby (z $=$ 0.016), on-going merger cluster, Abell 3627. The overall temperature of the ICM is around 7 keV, and we found a cool region with $kT$$\sim$ 4–5 keV at the position corresponding to the brightness excess from a spherically symmetrical $\beta$-model found by ROSAT. This structure seems to be a subcluster colliding into the main body. In the temperature and density profiles, no apparent jump associated with a shock is confirmed at the colliding position; therefore, the velocity of the subcluster seems to be subsonic. On the other hand, the line-of-sight velocity of the subcluster is strictly restricted to be less than 800 km s$^{-1}$ using the Doppler shift of the Fe-K lines. Moreover, our ICM temperature map also suggests the possibility of another merging subcluster in the north-west region. A 3627 is now in the process of an aggressive cluster merger, associated with the formation of a large-scale structure.
Video Observation of the Leonids 2001 Activity
Authors: Lin Chilong , Abe Shinsuke , Koten Pavel , Yang I-Ching
Published: March 2014

This paper presents an analysis of records obtained by video equipment of the 2001 Leonid meteor storm. Totally, 3712 meteors, including 22 non-Leonid ones, were recognized from the record of 247 min. The brightness of meteors was measured with the software “LIMovie”, and a population index of $r$$=$ 2.01$\ \pm\ $0.05 ($-$8 $\le$ mag $\le$$-$3) was thus derived. We proposed a way to derive the mass-distribution index, $s$$=$ 1.82, from only our one-station data. The maximum of the activity appeared at 18$^{\rm h}$25$^{\rm m}$ UT with an effective peak of ZHR$_{90^{\circ}\times67^{\circ}}$$=$ 52606 (mag $\le$$+$6.5). There are also compatible sub-peaks and high plateaus beside the main peak. One of them may correspond to the predicted 9-revolution dust trail (ejection in 1699). In this article we treat the cross section of the influx zone as a trapezoid. The peak “influx rate” generated by the 4-revolution dust trail (ejection in 1866) thus derived would be 6.76 $\times$ 10$^{-5}\ $km$^{-2}\ $s$^{-1}$ (mag $\le$$+$6.5), and the corresponding “spatial number density” would be 9.52 $\times$ 10$^{-7}\ $km$^{-3}$ (mag $\le$$+$6.5).