bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotation Modulations and Distributions of the Flare Occurrence Rates on the Surface of Five UV Ceti Type Stars
Authors: Dal Hasan Ali , Evren Serdar
Published: March 2014

In this study, we considered stellar spots, stellar flares, and also the relation between these two magnetic proccesses that take place on UV Cet stars. In addition, the hypothesis about slow flares described by Gurzadyan (1986 Ap&SS, 125, 127) was investigated. All of these discussions were based on the results of three years of observations of UV Cet-type stars: AD Leo, EV Lac, V1005 Ori, EQ Peg, and V1054 Oph. First of all, the results show that stellar spot activity occurs on the stellar surface of EV Lac, V1005 Ori, and EQ Peg, while AD Leo does not show any short-term variability and V1054 Oph does not exhibit any variability. We report on new ephemerides for EV Lac, V1005 Ori, and EQ Peg, obtained from time-series analyses. The phases, computed at intervals of 0.10 phase length, where the mean flare occurence rates to obtain maximum amplitude; also, the phases of rotational modulation were compared in order to investigate whether there is any longitudinal relation between stellar flares and spots. Although the results show that flare events are related with spotted areas on stellar surfaces during some of the observing seasons, we did not find any clear correlation among them. Finally, it was tested whether slow flares are fast flares occurring on the opposite side of the stars according to the direction of the observers, as mentioned in a hypothesis developed by Gurzadyan (1986). The flare occurence rates reveal that both slow and fast flares can occur in any rotational phases. The flare occurence rates of both fast and slow flares vary in the same way along the longitudes for all program stars. These results are not expected based on the case mentioned in the hypothesis.
Early Results of the 3 mm Spectral Line Survey toward the Lynds 1157 B1 Shocked Region
Authors: Sugimura Mika , Yamaguchi Takahiro , Sakai Takeshi , Umemoto Tomofumi , Sakai Nami , Takano Shuro , Aikawa Yuri , Hirano Naomi , Liu Sheng-Yuan , Millar T. J. , Nomura Hideko , Su Yu-Nung , Takakuwa Shigehisa , Yamamoto Satoshi
Published: March 2014

We have conducted a sensitive 3 mm observation toward the shocked region, Lynds 1157 B1, which is an interaction spot between a molecular outflow and its ambient gas. We have successfully detected the CH$_3$CHO, HCOOCH$_3$, and HCOOH lines, as well as the CH$_2$DOH line. The abundances of these molecules relative to CH$_3$OH are found to be lower than those in the low-mass star-forming core, IRAS 16293$-$2422. Since these molecules are thought to evaporate from grain mantles, the observational results mean that complex molecules are less abundant in grain mantles residing in the ambient cloud surrounding a prestellar/protostellar core. Instead, efficient formation of the complex organic species and deuterated species should take place in a prestellar/protostellar core. The present result verifies the importance of an unbiased line survey of this source.
Absorption-Line Survey of H$_3^\textbf{+}$ toward the Galactic Center Sources. III. Extent of Warm and Diffuse Clouds
Authors: Goto Miwa , Usuda Tomonori , Geballe Thomas R. , Indriolo Nick , Mccall Benjamin J. , Henning Thomas , Oka Takeshi
Published: March 2014

We present a follow-up observation on Geballe and Oka (2010, ApJ, 709, L70), who found high column densities of H$_3^+$  $\sim$ 100 pc apart from the Galactic center on the lines of sight to 2MASS J17432173$-$2951430 (J1743) and 2MASS J17470898$-$2829561 (J1747). The wavelength coverages on these sightlines have been extended in order to observe two key transitions of H$_3^+$ — $R$(3, 3)$^l$ and $R$(2, 2)$^l$ — which constrain the temperature and density of the environment. The profiles of the H$_3^+$  $R$(3, 3)$^l$ line, which is due only to gas in the Galactic center, closely match the differences between the H$_3^+$  $R$(1, 1)$^l$ and CO line profiles, just as they do for previously studied sightlines in the Galactic center. Absorption in the $R$(2, 2)$^l$ line of H$_3^+$ is present in J1747 at velocities of between $-$60 and $+$100 km s$^{-1}$. This is the second clear detection of this line in the interstellar medium after GC IRS 3 in the Central cluster. The temperature of the absorbing gas in this velocity range is 350 K, significantly warmer than that of diffuse clouds in other parts of the Central Molecular Zone. This indicates that the absorbing gas localizes on the Sgr B molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005, ApJ, 632, 882) apparently extends to $\sim$100 pc, but there is a hint that its temperature is somewhat lower in the line of sight to J1743 than elsewhere in the Galactic center. The observation of H$_3^+$ toward J1747 is compared with the recent Herschel observation of H$_2$O$^+$ toward Sgr B2, and their chemical relation and remarkably similar velocity profiles are discussed.
Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization
Authors: Ikejiri Yuki , Uemura Makoto , Sasada Mahito , Ito Ryosuke , Yamanaka Masayuki , Sakimoto Kiyoshi , Arai Akira , Fukazawa Yasushi , Ohsugi Takashi , Kawabata Koji S. , Yoshida Michitoshi , Sato Shuji , Kino Masaru
Published: March 2014

We report on the correlation between the flux, color, and polarization variations on time scales of days–months in blazars, and discuss their universal aspects. We performed monitoring of 42 blazars in the optical and near-infrared bands from 2008 to 2010 using TRISPEC attached to the ``Kanata'' 1.5-m telescope. We found that 28 blazars exhibited ``bluer-when-brighter'' trends in their whole or a part of time-series data sets. This corresponds to 88% of objects that were observed for $\gt\ $10 days. Thus, our observation unambiguously confirmed that the ``bluer-when-brighter'' trend is common in the emission from blazar jets. This trend was apparently generated by a variation component with a constant and relatively blue color and an underlying red component. Prominent short-term flares on time scales of days–weeks tended to exhibit a spectral hysteresis; their rising phases were bluer than their decay phases around the flare maxima. In contrast to the strong flux–color correlation, the correlation of the flux and polarization degree was relatively weak; only 10 objects showed significant positive correlations. Rotations of polarization were detected only in three objects: PKS 1510$-$089, 3C 454.3, and PKS 1749$+$096, and possibly in S5 0716$+$714. We also investigated the dependence of the degree of variability on the luminosity and the synchrotron peak frequency, $\nu _{\rm peak}$. As a result, we found that lower luminosity and higher $\nu _{\rm peak}$ objects had smaller variations in their amplitudes both in the flux, color, and polarization degree. Our observation suggests the presence of several distinct emitting sources, which have different variation time-scales, colors, and polarizations. We propose that the energy injection by, for example, internal shocks in relativistic shells is a major factor for blazar variations on time scales of both days and months.
Annual Parallax Measurements of an Infrared Dark Cloud, MSXDC G034.43+00.24 with VERA
Authors: Kurayama Tomoharu , Nakagawa Akiharu , Sawada-Satoh Satoko , Sato Katsuhisa , Honma Mareki , Sunada Kazuyoshi , Hirota Tomoya , Imai Hiroshi
Published: March 2014

We have measured the annual parallax of the H$_{2}$O maser source associated with an infrared dark cloud, MSXDC G034.43$+$00.24, from observations with VERA (VLBI Exploration of Radio Astrometry). The parallax is 0.643$\ \pm\ $0.049 mas, corresponding to a distance of 1.56$^{+0.12}_{\-0.11}\ $kpc. This value is less than half of the previous kinematic distance of 3.7 kpc. We revised the core-mass estimates of MSXDC G034.43$+$00.24, based on the virial masses, LTE masses and dust masses, and showed that the core masses decrease from the previous estimations of $\sim\ $1000$\ M_\odot$ to hundreds of $\ M_\odot$. The spectral type derived from the luminosity also changes from O9.5 to B1 in the case of MM1. This spectral type is still consistent with that of the massive star. The radial velocity derived from the flat rotation model is smaller than the observed velocity, which corresponds to a peculiar motion of $\sim\ $40 km s$^{-1}$ in the line-of-sight direction.
X-Ray Spectrum of a Peculiar Supernova Remnant, G 359.1-0.5
Authors: Ohnishi Takao , Koyama Katsuji , Tsuru Takeshi Go , Masai Kuniaki , Yamaguchi Hiroya , Ozawa Midori
Published: March 2014

We present Suzaku results of a supernova remnant (SNR), G 359.1$-$0.5, in the direction of the Galactic center region. From the SNR, we have found prominent K-shell lines of highly ionized Si and S ions, together with unusual structures at 2.5–3.0 and 3.1–3.6 keV. No canonical SNR plasma model, in either ionization equilibrium or under-ionization, can explain the structures. The energies and shapes of the structures are similar to those of the radiative transitions of free electrons to the K-shell of He-like Si and S ions (radiative recombination continuum: RRC). The presence of strong RRC structures indicates that the plasma is in over-ionization. In fact, the observed spectrum has been well-fitted with an over-ionized plasma model. The best-fit electron temperature of 0.29 keV is far smaller than the ionization temperature of 0.77 keV, which means that G 359.1$-$0.5 is in an extreme condition of over-ionization. We report some cautions on the physical parameters, and comment about possible origins for the over-ionized plasma.
K-Shell Emission of Neutral Iron Line from Sagittarius B2 Excited by Subrelativistic Protons
Authors: Dogiel Vladimir , Chernyshov Dmitrii , Koyama Katsuji , Nobukawa Masayoshi , Cheng Kwong-Sang
Published: March 2014

We investigated the emission of the K$\alpha$ iron line from massive molecular clouds in the galactic center (GC). We assumed that at present the total flux of this emission consists of a time-variable component generated by primary X-ray photons ejected by Sagittarius A$^\ast$ (Sgr A$^\ast$) in the past, and a relatively weak quasi-stationary component excited by the impact of protons that were generated by star accretion onto the central black hole. The level of background emission was estimated from a rise of the 6.4 keV line intensity in the direction of several molecular clouds, which we interpreted as being a stage when the X-ray front ejected by Sgr A$^\ast$ entered into these clouds. Regarding the 6.4 keV emission before this intensity jump, we interpreted it as emission generated by subrelativistic cosmic rays there. The cross-section of K$\alpha$ vacancies produced by protons differs from that of electrons or X-rays. Therefore, we expect that this processes can be distinguished from an analysis of the equivalent width of the iron line; also, the time variations of the width can be predicted. The line intensity from the clouds depends on their distance from Sgr A$^\ast$ and the coefficient of spatial diffusion near the galactic center. We expect that in a few years the line intensity for the cloud G 0.11$-$0.11, which is relatively close to Sgr A$^\ast$, will decrease to a level of $\lesssim\ $10% from its present value. For the cloud Sagittarius B2 (Sgr B2) the situation is more intricate. If the diffusion coefficient is $D$$\gtrsim$ 10$^{27}\ $cm$^{2}\ $s$^{-1}$, the expected stationary flux should be about 10% of its level in 2000. In the opposite case the line intensity from Sgr B2 should drop down to zero because the protons do not reach the cloud.
Running Umbral Waves Observed with Hinode
Authors: Liang Hongfei , Ma Li , Yang Rujuan , Li Haidong , Zhao Li
Published: March 2014

Observations of the main sunspot of NOAA 10953 were carried out with the Solar Optical Telescope aboard Hinode with the line Ca II H on 2007 April 30. The high-cadence (up to 10 s) Ca II H intensity images permit us to elaborate on the nature of umbral oscillations. It is found there are 19 wave sources within the sunspot and 82 running umbral waves that periodically appear at the wave sources, and propagate outward while forming ellipses or partial arcs. Due to their own expansion, the running waves become more diffused, and eventually disappear at the edge of the umbra. On the basis of the time-interval distribution between adjacent running waves being centered close to 144 s, we observed an approximate oscillation period of 142 s. By tracing the fronts of the running waves, the propagation speed of the running waves ranges from 30 to 45 km s$^{-1}$. The distribution for all running waves has an average propagation speed of $\sim$ 37.4 km s$^{-1}$. Furthermore, we have found an interesting phenomenon that implies there may be interaction of a microflare with some running umbral waves.
Resonant Excitation of Disk Oscillations in Deformed Disks. V. Effects of Dissipative Process
Authors: Kato Shoji
Published: March 2014

It is suggested that a set of positive- and negative-energy oscillations can be resonantly excited in the inner region of deformed (warped or eccentric) relativistic disks. In this paper we examine how a dissipative process affects this wave excitation. The results show that when the resonant condition in frequency is roughly satisfied, and thus the oscillations are excited, the introduction of a dissipative process works so as to decrease the growth rate of the oscillations. When the frequency difference between the two oscillations is larger than a certain amount that is required by the resonant condition, however, the oscillations are excited by introducing a dissipative process. This excitation by the dissipative process can be understood as a special example of a double-diffusive instability.
ImprovedEp-TL-Lp Diagram and a Robust Regression Method
Authors: Tsutsui Ryo , Nakamura Takashi , Yonetoku Daisuke , Murakami Toshio , Morihara Yoshiyuki , Takahashi Keitaro
Published: March 2014

The accuracy and reliability of gamma-ray bursts (GRBs) as distance indicators are strongly restricted by their systematic errors, which are larger than the statistical errors. These systematic errors might come from either intrinsic variations of GRBs, or systematic errors in observations. In this paper, we consider the possible origins of systematic errors in the following observables: (i) the spectral peak energies ($E_{\rm p}$) estimated by the cut-off power law (CPL) function and (ii) the peak luminosities ($L_{\rm p}$) estimated by 1 s in observer time. By removing or correcting them we can reveal the true intrinsic variation of the $E_{\rm p}$–$T_{\rm L}$–$L_{\rm p}$ relation of GRBs. Here, $T_{\rm L}$ is the third parameter of GRBs, defined as $T_{\rm L}$$\equiv$$E_{\rm iso} / L_{\rm p}$. Not only the time resolution of $L_{\rm p}$ is converted from the observer time to the GRB rest frame time, the time resolution with the largest likelihood is sought. After removing any obvious origin of systematic errors in the observation mentioned above, there still seems to remain some outliers. For this reason, we take of account another origin of the systematic error, as below: (iii) the contamination of short GRBs or other populations. To estimate the best-fit parameters of the $E_{\rm p}$–$T_{\rm L}$–$L_{\rm p}$ relations from data including outliers, we develop a new method which combines robust regression and an outlier identification technique. Using our new method for 18 GRBs with $\sigma_{E_{\rm p}}/E_{\rm p}$$\lt$ 0.1, we detected 6 outliers, and found that the $E_{\rm p}$–$T_{\rm L}$–$L_{\rm p}$ relation becomes tightest at around 3 s.
A New Method of Dark-Current Estimation for Diffuse Sky Measurements with the AKARI Infrared Camera
Authors: Tsumura Kohji , Wada Takehiko
Published: March 2014

We developed a new method for estimating the dark current of near-infrared (NIR) data from the Infra-Red Camera (IRC) aboard the AKARI satellite. The existing method of dark-current estimation is insufficient because the dark current is enhanced by charged particles hitting the detector in the South Atlantic Anomaly (SAA). We could trace this dark-current drift even during astronomical observations by monitoring the dark current in the masked region on the focal plane of IRC. We analyzed approximately 4500 dark frames, and found a relation in the integrated dark charge between the masked region and the exposed one of the detector array. Using this relation, we can estimate the integrated dark charge at each pixel from the average integrated dark charge in the masked region even during astronomical observations. Residuals in our new method were shown to be approximately 1 ADU (corresponding to 3 nW m$^{-2}$sr$^{-1}$ for the N2 band), even for the SAA-enhanced case, which is better than those in any existing methods by five or more times.
Near-Ultraviolet and Visible Spectroscopy of HAYABUSA Spacecraft Re-Entry
Authors: Abe Shinsuke , Fujita Kazuhisa , Kakinami Yoshihiro , Iiyama Ohmi , Kurosaki Hirohisa , Shoemaker Michael A. , Shiba Yasuo , Ueda Masayoshi , Suzuki Masaharu
Published: March 2014

HAYABUSA is the first spacecraft ever to land on and lift off from any celestial body other than the moon. The mission, which returned asteroid samples to the Earth while overcoming various technical hurdles, ended on 2010 June 13, with the planned atmospheric re-entry. In order to safely deliver the sample return capsule, the HAYABUSA spacecraft ended its 7-year journey in a brilliant ``artificial fireball'' over the Australian desert. Spectroscopic observation was carried out in the near-ultraviolet and visible wavelengths between 3000 Å and 7500 Å at 3–20 Å resolution. Approximately 100 atomic lines such as Fe i, Mg i, Na i, Al i, Cr I, Mn i, Ni i, Ti i, Li i, Zn i, O i, and N i were identified from the spacecraft. Exotic atoms such as Cu i, Mo i, Xe i and Hg i were also detected. A strong Li i line (6708 Å) at a height of $\sim\ $55 km originated from the onboard Li-Ion batteries. The FeO molecule bands at a height of $\sim\ $63 km were probably formed in the wake of the spacecraft. The effective excitation temperature as determined from the atomic lines varied from 4500 K to 6000 K. The observed number density of Fe i was about 10 times more abundant than Mg i after the spacecraft explosion. N$_{2}^{+}$ ($1^-$) bands from a shock layer and CN violet bands from the sample return capsule's ablating heat shield were dominant molecular bands in the near-ultraviolet region of 3000–4000 Å. OH($A$–$X$) band was likely to exist around 3092 Å. A strong shock layer from the HAYABUSA spacecraft was rapidly formed at heights between 93 km and 83 km, which was confirmed by detection of N$_{2}^{+}$ ($1^-$) bands with a vibration temperature of $\sim\ $13000 K. Gray-body temperature of the capsule at a height of $\sim\ $42 km was estimated to be $\sim\ $2437 K which is matched to a theoretical prediction. The final message of the HAYABUSA spacecraft and its sample return capsule are discussed through our spectroscopy.
Temperature Variations of Cold Dust in the Triangulum Galaxy M 33
Authors: Komugi Shinya , Tosaki Tomoka , Kohno Kotaro , Tsukagoshi Takashi , Nakanishi Kouichiro , Sawada Tsuyoshi , Kawabe Ryohei , Ezawa Hajime , Kuno Nario , Onodera Sachiko , Tamura Yoichi , Wilson Grant W. , Yun Min S. , Scott Kimberly S. , Perera Thushara A. , Austermann Jason E. , Hughes David H. , Aretxaga Itziar , Tanaka Kunihiko , Muraoka Kazuyuki , Miura Rie , Egusa Fumi
Published: March 2014

We present wide-field 1.1 mm continuum imaging of the nearby spiral galaxy M 33, conducted with the AzTEC bolometer camera on ASTE. We show that the 1.1 mm flux traces the distribution of dust with $T$  $\sim$ 20 K. Combined with far-infrared imaging at 160$\ \mu$m, we derived the dust temperature distribution out to a galactic radius of $\sim$ 7 kpc with a spatial resolution of $\sim$ 150 pc. Although the 1.1 mm flux was observed predominantly near star-forming regions, we found a smooth radial temperature gradient declining from $\sim$ 20 K to $\sim$ 13 K consistent with recent results from the Herschel satellite. Further comparisons of individual regions show a strong correlation between the cold dust temperature and the $K_{\rm S}$ band brightness, but not with the ionizing flux. The observed results imply that the dominant heating source of cold dust at few hundred parsec scales is due to non-OB stars, even when associated with star-forming regions.
Expedition for a Ground-Based Observation of HAYABUSA Spacecraft Re-Entry
Authors: Watanabe Jun-ichi , Ohkawa Takuya , Sato Mikiya , Ohnishi Kouji , Iijima Yutaka , Kagaya Yutaka , Tanabe Tsutomu
Published: March 2014

The HAYABUSA spacecraft re-entered the Earth’s atmosphere on 2010 June 13 UT, together with the capsule for the sample return. This was the first trial of the re-entry experiment as a Japanese interplanetary spacecraft. We undertook an expedition to South Australia for ground-based observations, and succeeded in obtaining valuable data of various phenomena occurring at this re-entry. Our data were widely used not only for scientific analysis, but also for outreach purposes. This paper provides an overview of our expedition.
Trajectory of HAYABUSA Reentry Determined from Multisite TV Observations
Authors: Ueda Masayoshi , Shiba Yasuo , Yamamoto Masa-yuki , Fujita Kazuhisa , Watanabe Jun-ichi , Sato Mikiya , Abe Shinsuke , Kakinami Yoshihiro , Uehara Satoshi , Okamoto Sadao , Fujiwara Yasunori , Tanabe Tsutomu
Published: March 2014

The asteroid explorer HAYABUSA reentered into the Earth's atmosphere on 2010 June 13. We made simultaneous TV (television) observations at seven ground sites in order to calculate the trajectories of HAYABUSA and its sample return capsule (SRC), which both reentered into the atmosphere. Our TV observations showed that, after HAYABUSA reentered the atmosphere, the beginning time of its light emission on video was 13:51:57.4 UT at a height of 101.0$\ \pm\ $0.2 km. The end time was 13:52:42.0 UT at a height of 38.6$\ \pm\ $0.2 km. The initial velocity at the beginning was 12.1$\ \pm\ $0.3 km s$^{-1}$, and the entry angle was 9$^{\circ}$. After identifying SRC as separated light emission independent of the mother spacecraft, we analyzed the trajectory of SRC from a height of 52.9 km to 35.7 km based on video images. The actual trajectory of the capsule, determined from the TV observations, was almost the same as the predicted trajectory in terms of the position, velocity, and time. We then calculated the fall spots of the SRC heat shields from the multisite TV observations.
Detection of Acoustic/Infrasonic/Seismic Waves Generated by Hypersonic Re-Entry of the HAYABUSA Capsule and Fragmented Parts of the Spacecraft
Authors: Yamamoto Masa-yuki , Ishihara Yoshiaki , Hiramatsu Yoshihiro , Kitamura Kazuki , Ueda Masayoshi , Shiba Yasuo , Furumoto Muneyoshi , Fujita Kazuhisa
Published: March 2014

Acoustic/infrasonic/seismic waves were observed during the re-entry of the Japanese asteroid explorer “HAYABUSA” at 6 ground sites in Woomera, Australia, on 2010 June 13. Overpressure values of infrasound waves were detected at 3 ground sites in a range from 1.3 Pa, 1.0 Pa, and 0.7 Pa with each distance of 36.9 km, 54.9 km, and 67.8 km, respectively, apart from the SRC trajectory. Seismic waveforms through air-to-ground coupling processes were also detected at 6 sites, showing a one-to-one correspondence to infrasound waves at all simultaneous observation sites. Audible sound up to 1 kHz was recorded at one site with a distance of 67.8 km. The mother spacecraft was fragmented from 75 km down to 38 km with a few explosive enhancements of emissions. A persistent train of HAYABUSA re-entry was confirmed at an altitude range of between 92 km down to 82 km for about 3 minutes. Light curves of 136 fragmented parts of the spacecraft were analyzed in detail based on video observations taken at multiple ground sites, being classified into three types of fragmentations, i.e., melting, explosive, and re-fragmented types. In a comparison between infrasonic waves and video-image analyses, regarding the generation of sonic-boom type shock waves by hypersonically moving artificial meteors, both the sample return capsule and fragmented parts of the mother spacecraft, at an altitude of 40$\ \pm\ $1 km were confirmed with a one-to-one correspondence with each other.
Black-Hole Shadow Has Infinite Optical Depth
Authors: Fukue Jun
Published: March 2014

When a black hole is surrounded by a geometrically thin standard disk, we would observe a black-hole silhouette, whose edge is an innermost stable circular orbit. When it is surrounded by a geometrically thick supercritical disk, the central black hole would be self-occulted by the disk itself and massive winds. When it is covered by an optically thin plasma, on the other hand, a black-hole shadow would be seen, and observations of the black-hole shadow is now desired. If the optically thin plasma is freely infalling, however, we find that the optical depth in the radial direction becomes infinite due to the relativistic effect. Hence, the physical meanings of the black-hole shadow should be re-interpreted, although the shadow would be seen.
NRO M 33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC). I. H I to H2 Transition
Authors: Tosaki Tomoka , Kuno Nario , Onodera Sachiko , Miura Rie , Sawada Tsuyoshi , Muraoka Kazuyuki , Nakanishi Kouichiro , Komugi Shinya , Nakanishi Hiroyuki , Kaneko Hiroyuki , Hirota Akihiko , Kohno Kotaro , Kawabe Ryohei
Published: March 2014

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

Radiative transfer in a geometrically thin accretion disk with finite optical depth is reconsidered under a non-gray treatment, while focusing attention on the scattering effect. The emergent intensity as well as other radiative quantities are analytically obtained in simple and uniform-heating cases. In the simple case with a given Planck function, for a vertically isothermal atmosphere, the scattering effect is important, and the emergent intensity becomes a modified blackbody spectrum, as in many of the traditional cases. For a non-isothermal atmosphere, however, the scattering effect is not important, but the emergent intensity is mainly affected by the disk optical depth. In the case with uniform heating, the scattering effect is not important, as long as the disk optical depth is sufficiently large. For a finite optical depth, however, we find that the combination effect of the scattering and the finite optical depth drastically change the emergent intensity and the radiative quantities. Since the accretion disk is generally non-isothermal in the vertical direction, or has a finite optical depth, we should carefully calculate the disk spectra, while taking into account radiative transfer in the disk.
Stochastic Acceleration of Cosmic Rays in the Central Molecular Zone of the Galaxy
Authors: Amano Takanobu , Torii Kazufumi , Hayakawa Takahiro , Fukui Yasuo
Published: March 2014

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

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

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

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

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

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

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

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

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

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

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

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

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

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