bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Energy Electrons in Double-Loop Flares
Authors: Hanaoka Yoichiro
Published: March 2014

We studied the fast temporal variations in the brightness of the radio and hard X-ray sources of three double-loop flares. In such flares, the main radio/hard X-ray source is located near to one of the footpoints of a large overlying loop, where a small, newly emerging loop appears and the two loops interact, and the remote source is located at another footpoint of the large loop. The following results were obtained from the analysis: (1) The main source and the remote source basically show a correlated brightness fluctuation, but the rapid fluctuation of the brightness of the remote source lags behind that of the main source for about 500 ms. This result is evidence that the electron-acceleration region is close to the main source and, therefore, it is most presumable that the high-energy electrons in the double-loop flares are accelerated in the interaction region of the two loops. (2) The brightness of the hard X-rays from the main source and that of the microwaves from the remote source fluctuate highly, but the microwaves from the main source fluctuate less. This result means that the microwave-emitting electrons are effectively trapped at the main source region.
Optically Thick Wind Solutions for an Extremely Rapid Light Curve of Recurrent Novae
Authors: Kato Mariko
Published: March 2014

Wind mass-loss solutions and theoretical light curves for rapid outbursts of recurrent novae are presented for a wide range of parameters of white-dwarf masses of 1.2, 1.3, 1.35, and 1.377 M® with envelope compositions of X=0.7, 0.35, and 0.1 and heavy element contents of Z=0.001, 0.004, 0.01, 0.02, 0.05, and 0.1. Very rapid optical decline (£3 < 10 days) is obtained only in very massive white dwarfs ( > 1.35 M® ) for Z=0.02. Systematic differences of evolutionary time-scale and of the wind velocity are predicted between novae of Populations I and II. The light-curve fittings of four recurrent novae U Sco, V394 CrA, T CrB, and V745 Sco, show that these systems contain a very massive white dwarf of mass 1.35–1.38 M®.
FTS Measurements of Submillimeter-Wave Atmospheric Opacity at Pampa la Bola II : Supra-Terahertz Windows and Model Fitting
Authors: Matsushita Satoki , Matsuo Hiroshi , Pardo Juan R. , Radford Simon J. E.
Published: March 2014

A second observing run aimed to measure the millimeter and submillimeter-wave (150–1500 GHz or 2 mm–200 μm) atmospheric opacity was carried out with a Fourier Transform Spectrometer (FTS) at Pampa la Bola, 4800 m above sea level in northern Chile. We obtained high transmission spectra, showing up to ∼ 67% transmission at submillimeter-wave windows. The observed spectra can be well modeled by newly developed radiative-transfer calculations. Correlations between 220 GHz and submillimeter-wave opacities were reanalized, including the new data set. The results show almost identical trends as the ones resulting from the first measurements. We also identified supra-terahertz windows (located around 1035 GHz, 1350 GHz, and 1500 GHz), which could not be seen in our first measurements. Opacity correlations between the 220 GHz and these new windows are derived for the first time. Combined with a statistical study of the 225 GHz opacity data of the Chajnantor site (7 km apart from Pampa la Bola), it is estimated that submillimeter-wave observations can be done with zenith opacity less than 1.0 (at the most transparent frequency in those windows) for about 50% of the winter season.
ASCA Observations of Two Ultra-Luminous Compact X-Ray Sources in the Edge-On Spiral Galaxy NGC 4565
Authors: Mizuno Tsunefumi , Ohnishi Tomohisa , Kubota Aya , Makishima Kazuo , Tashiro Makoto
Published: March 2014

The edge-on spiral galaxy NGC 4565 was observed for ∼ 35 ks with ASCA in the 0.5–10 keV energy band. The X-ray emission was dominated by two bright sources, which could be identified with two point-like X-ray sources seen in the ROSAT HRI image. The observed 0.5–10 keV fluxes of these sources, 1.7 × 10−12 erg s−1 cm−2 and 0.7 × 10−12 erg s−1 cm−2, imply bolometric luminosities of 1.2 × 1040 erg s−1 and 4.6 × 1039 erg s−1, respectively. They exhibit similar spectra, which can be explained by emission from optically thick accretion disks with inner-disk temperature of 1.4–1.6 keV. One of them, coincident in position with the nucleus, shows too low absorption to be the active nucleus seen through the galaxy disk. Their spectra and high luminosities suggest that they are both mass-accreting black-hole binaries. However, the black-hole mass required by the Eddington limit is rather high (≥ 50 M⊙), and the observed disk temperature is too high to be compatible with the high black-hole mass. Several attempts have been made to solve these problems.
Distribution and Kinematics of the Molecular Clouds in the Gum Nebula
Authors: Yamaguchi Nobuyuki , Mizuno Norikazu , Moriguchi Yoshiaki , Yonekura Yoshinori , Mizuno Akira , Fukui Yasuo
Published: March 2014

We have made an extensive search for molecular gas toward the Gum Nebula in the J = 1−0 12CO emission at 2.6 mm. The 12CO distribution has been used to identify 82 molecular clouds at |b| > 5°, including those toward optically visible cometary globules which are likely to be associated with the Nebula. Their velocity is significantly deviated from the galactic rotation and the velocity dispersion is as large as ∼ 20 km s-1, indicating that they are expanding under the dynamical effects of OB stars and/or supernova explosions. The total mass of these molecular clouds is estimated to be ∼ 1.7 × 104M⊙, corresponding to ∼ 10% of the H I gas associated with the nebula. Most of these molecular clouds are well explained as part of a supershell of ∼ 70–130 pc radius that is expanding at 10–15 km s-1. The total kinetic energy of this shell will require a total energy deposit of ∼ (2.1–4.7) × 1050 erg as the stellar winds and/or the supernova explosions. The massive stars in this region are quantitatively examined as candidates that have supplied this energy.
Galaxy Formation from a Low-Spin Density Perturbation in a CDM Universe
Authors: Kawata Daisuke
Published: March 2014

In order to understand the formation process of elliptical galaxies which are not rotationally supported, we carried out numerical simulations of galaxy formation from a density perturbation with a rotation corresponding to a small spin parameter. The three-dimensional TREE N-Body/SPH simulation code used included dark matter and gas dynamics, radiative cooling, star formation, supernova feedback, and metal enrichment. The initial condition was a slowly rotating, top-hat over-dense sphere on which the perturbations expected in a cold dark matter (CDM) universe were superposed. By means of a stellar-population synthesis, we calculated the surface-brightness profile, the metallicity distribution, and the photometric properties of the end-product, and found that these properties quantitatively agree with the observed properties of bright elliptical galaxies. Thus, we conclude that, in a CDM universe, a proto-galaxy having a spin-parameter as small as 0.02 evolves into an elliptical galaxy.
150 GHz NOBA Observations of the Galactic Center Arc
Authors: Reich Wolfgang , Sofue Yoshiaki , Matsuo Hiroshi
Published: March 2014

We have used the seven-beam 150 GHz bolometer NOBA installed at the Nobeyama 45-m telescope to map the central section of the Galactic Center Arc. In addition, we mapped Sgr A, which shows Sgr A* and the thermal spiral structure. The results agree with previous mm-observations. South of the thermal “sickle” feature (G0.18-0.04) we observed three regions of enhanced emission along the Arc, which are located slightly offset relative to the most intense vertical filaments seen at low frequencies. This 150 GHz emission is observed at the apparent interacting areas of dense molecular material with the Arc. Another structure is seen south of the molecular cloud, where the Arc's vertical filaments apparently cross a weak filamentary structure running orthogonally in the direction of Sgr A. The 150 GHz results are unexpected in view of previous 32 GHz and 43 GHz results, which indicate a fading of the Arc towards higher frequencies. Cold dust can be ruled out as the origin of the 150 GHz emission. Synchrotron emission from quasi-monoenergetic electrons or an electron distribution with a low-energy cut-off seems to be compatible with the available data. The coincidence of enhanced emission with regions of interacting molecular gas strongly suggests that high-energy electrons are accelerated in those places where the magnetic field is compressed, and subsequently enter and illuminate the Arc.
Discovery of a New SU UMa-Type Dwarf Nova, V 1028 Cygni
Authors: Baba Hajime , Kato Taichi , Nogami Daisaku , Hirata Ryuko , Matsumoto Katsura , Sadakane Kozo
Published: March 2014

V-band high-speed CCD photometry of V 1028 Cyg revealed that hump structures existed in the early stage of its 1995 July outburst. We obtained 0.06154 (± 0.00002) d as the best estimated period of superhumps. We confirmed that this dwarf nova belongs to the SU UMa stars. A re-brightening occurred after the superoutburst, and may be associated with a normal outburst. An analysis of the timings of superhump maxima showed clear evidence for an increase of the superhump period (Pdot = Ṗ/P) with 7.54 × 10−6. Only a few stars (AL Com, T Leo, SW UMa, etc.) are reported to have such an increase of the superhump period. At the end of the superoutburst, we detected that the amplitude of the superhumps increased considerably. Both of these properties are not typical features of ordinary SU UMa stars. The connection between the WZ Sge-type and the SU UMa-type dwarf novae is briefly discussed.
Upper Limits of Iron Line Flux in X-Ray Afterglow of Two Gamma-Ray Bursts with ASCA
Authors: Yonetoku Daisuke , Murakami Toshio , Ueda Yoshihiro , Ishida Manabu , Yoshida Atsumasa , Kawai Nobuyuki , Shirasaki Yuji , Tsuru Takeshi Go , Uno Shin'ichiro
Published: March 2014

The iron emission line in the X-ray afterglow spectra of a Gamma-Ray Burst is thought to be a key to understanding the environment of progenitors. Although two independent observations with BeppoSAX and ASCA reported strong red-shifted iron emission line, the statistical significance of these detections was not very high. Further observations were expected and two more GRBs, GRB 990123 and GRB 990704, were observed with the X-ray satellite ASCA in 1999. The spectra of these two afterglows can be explained by a simple power-law model with excess absorption, but without any iron emission-line feature. The 90% upper limit for the iron line flux is as low as FFe = 3.3 × 10−6 photons cm−2 s−1, or less than ∼ 100 eV in equivalent width (EW). This upper limit is an order-of-magnitude smaller than the previous two detections of 1–3 keV in EW.
Discovery and Photometric Observation of the Optical Counterpart of a Possible Galactic Halo X-Ray Transient, XTE J1118+480
Authors: Uemura Makoto , Kato Taichi , Matsumoto Katsura , Yamaoka Hitoshi , Takamizawa Kesao , Sano Yasuo , Haseda Katsumi , Cook Lewis M. , Buczynski Denis , Masi Gianluca
Published: March 2014

We discovered an optical counterpart of about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We performed astrometry and provided an accurate position of R.A. = 11h18m10s.85, Decl. = +48°02′12″.9. The outbursting object has been identified with a 18.8 mag star in the USNO catalog. Our pre-discovery data shows another outburst during 2000 January, again coinciding with an outburst detected in X-rays. Through CCD time-series photometry, we found the presence of a periodic variation with an amplitude of 0.055 mag and a period of 0.17078 ± 0.00004 d, which we consider to be a promising candidate of the orbital period. Because of the high galactic latitude and faint quiescence magnitude of 18.8, XTE J1118+480 is possibly the first firmly identified black hole candidate X-ray transient in the galactic halo.
A Spectral Index Map from VSOP Observations of Markarian 501
Authors: Edwards Philip G. , Giovannini Gabriele , Cotton William D. , Feretti Luigina , Fujisawa Kenta , Hirabayashi Hisashi , Lara Lucas , Venturi Tiziana
Published: March 2014

One of the features of VSOP observations is the ability to make contemporaneous, matched-resolution images at different frequencies in order to produce spectral index maps. We have combined VSOP observations made at 4.8 GHz on 1998 April 7 and 1.6 GHz on 1998 April 8 to make such a map of the variable X-ray and TeV gamma-ray source Mkn 501. The spectral index map reveals considerably more information than a single frequency total intensity image, and shows significant spectral variation along and across the milli-arcsecond scale jet. We interpret this in terms of models for the jet involving an inner fast spine and slower outer shear layer.
Dual-Frequency VSOP Observations of AO 0235+164
Authors: Frey Sándor , Gurvits Leonid I. , Altschuler Daniel R. , Davis Michael M. , Perillat Phil , Salter Chris J. , Aller Hugh D. , Aller Margo F. , Hirabayashi Hisashi
Published: March 2014

AO 0235+164 is a very compact, flat spectrum radio source identified as a BL Lac object at a redshift of z = 0.94. It is one of the most violently variable extragalactic objects at both optical and radio wavelengths. The radio structure of the source revealed by various ground-based VLBI observations is dominated by a nearly unresolved compact component at almost all available frequencies.

Dual-frequency space VLBI observations of AO 0235+164 were made with the VSOP mission in 1999 January-February. The array of the Japanese HALCA satellite and co-observing ground radio telescopes in Australia, Japan, China, and South Africa allowed us to study AO 0235+164 with an unprecedented angular resolution at frequencies of 1.6 and 5 GHz. We report on the sub-milliarcsecond structural properties of the source. The 5-GHz observations led to an estimate of TB>5.8×1013 K for the rest-frame brightness temperature of the core, which is the highest value measured with VSOP to date.
ASCA Identification of SMC X-2 with the 2.37-s Pulsar Discovered by RXTE
Authors: Yokogawa Jun , Torii Ken’ichi , Kohmura Takayoshi , Koyama Katsuji
Published: March 2014

ASCA observed a new X-ray pulsar recently discovered with RXTE in the Small Magellanic Cloud, and detected coherent pulsations with a barycentric period of $2.37230 \pm 0.00004~\mathrm{s}$. The position is determined within a $\sim 30{{}^{\mathrm{\prime\prime}}}$ radius error, which is much more accurate than that reported with RXTE. Since the position error well overlaps a $\sim 20{{}^{\mathrm{\prime\prime}}}$ radius error of the SAS-3 transient source SMC X-2, and since the probability that an unrelated source falls in the error region by chance is estimated to be less than 0.1%, we conclude that SMC X-2 is the 2.37-s pulsar. The X-ray spectrum in the 0.7–10.0 keV band can be fitted with a model of a power-law continuum plus a fluorescent line from neutral or low-ionization iron. The pulse profile has a single peak below a few keV and gradually changes to be a double-peaked structure as the energy increases; in particular, the iron line band (6.0–7.0 keV) marginally shows a double-peaked profile similar to that of the higher energy band observed with RXTE.
Temperature Map and Iron Abundance of the Ophiuchus Cluster of Galaxies
Authors: Watanabe Manabu , Yamashita Koujun , Furuzawa Akihiro , Kunieda Hideyo , Tawara Yuzuru
Published: March 2014

We present an X-ray surface-brightness distribution and a temperature map of the Ophiuchus cluster of galaxies observed by ASCA. The Ophiuchus cluster is a nearby rich cluster located at $ z= 0.028$ having an angular extent of $\sim 1 {{}^{\circ }}$. The observations were made by five pointings that cover the whole cluster. After deconvolution with the ASCA complex response function, we obtained the surface-brightness distribution with an angular resolution of $ {2{}^{\mathrm {\prime }}}$ and a temperature map with $ {8{}^{\mathrm {\prime }}}$ resolution. The X-ray surface-brightness distribution shows a nearly spherically symmetric distribution, except for a $ 15\sigma$ image excess at the position of $ {10{}^{\mathrm {\prime }}}$ to the north of the cluster center. On the other hand, a hot region with a temperature $ > 13 \,\mathrm{keV}$ is spread over a region of $ {20{}^{\mathrm {\prime }}}\times {30{}^{\mathrm {\prime }}}$ at $ {20{}^{\mathrm {\prime }}}$ to the west of the cluster center. Because these characteristics are similar to those of the Coma cluster, we conclude this cluster has never relaxed dynamically, and is also recently experienced a merger.
ASCA Observations of the Central Regions of M 31
Authors: Takahashi Hiromitsu , Okada Yuu , Kokubun Motohide , Makishima Kazuo
Published: March 2014

Using ASCA, spatially integrated X-ray spectra of the central regions of M 31 were studied. Data were accumulated over three different circular regions, with radii of $3', 6'$, and $12'$, all centered on the nucleus. The spectra are relatively similar among the three regions. In the energy range above 1.5 keV, the spectra are reproduced by a combination of a disk black-body component and a black-body component, implying that the emission mainly comes from an assembly of low-mass X-ray binaries. At energies below 1.5 keV, the spectra involve two additional softer components, expressed by thin-thermal plasma emission models of temperatures of $\sim 0.9 \,\mathrm{keV}$ and $\sim 0.3 \,\mathrm{keV}$. Over the central $12'$ (2.4 kpc) region and in the 0.5–10 keV energy band, the binary component has a luminosity of $2.6 \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$, while the two softer components both exhibit luminosities of $\sim 2 \times 10^{38} \,\mathrm{erg} \,\mathrm{s}^{-1}$. These results are compared with those from other missions, including Chandra and XMM-Newton in particular. A discussion is presented on the nature of the two softer spectral components besides the binary one.
Spiral Structure in WZ Sagittae around the 2001 Outburst Maximum
Authors: Baba Hajime , Sadakane Kozo , Norimoto Yuji , Ayani Kazuya , Ioroi Masayuki , Matsumoto Katsura , Nogami Daisaku , Makita Makoto , Kato Taichi
Published: March 2014

Intermediate-resolution phase-resolved spectra of WZ Sge were obtained on five consecutive nights (July 23–27) covering the initial stage of the 2001 superoutburst. Double-peaked emission lines of He II at 4686 Å, which were absent on July 23, emerged on July 24 together with emission lines of C III$/$ N III Bowen blend. Analyses of the He II emission lines using the Doppler tomography revealed an asymmetric spiral structure on the accretion disk. This finding demonstrates that spiral shocks with a very short orbital period can arise during the initial stage of an outburst and may be present in all SU UMa stars.
Detections of SiO Masers from the Large-Amplitude Variables in the Galactic Nuclear Disk
Authors: Imai Hiroshi , Deguchi Shuji , Fujii Takahiro , Glass Ian S. , Ita Yoshifusa , Izumiura Hideyuki , Kameya Osamu , Miyazaki Atsushi , Nakada Yoshikazu , Nakashima Jun-ichi
Published: March 2014

We have surveyed known large-amplitude variables within $ 15'$ of the Galactic center in the SiO $ J=1 \hbox{--} 0$$ v=1$ and 2 maser lines at 43 GHz, resulting in 79 detections and 58 non-detections. The detection rate of 58 percent is comparable to that obtained in Bulge IRAS source surveys. SiO lines were also detected from four other sources near the program objects. The SiO detection rate increases steeply with the period, particularly for stars with $P \gt 500 \,\mathrm{d}$$ P \gt 500 \,\mathrm{d}$, where it exceeds 80%. We found at a given period that the SiO detection rate is approximately double that for OH. These facts suggest that the large-amplitude variables in the Nuclear Disk region are AGB stars similar in their overall properties to the inner and outer bulge IRAS/SiO sources.
Rapid Optical Fluctuations in the Black Hole Binary V4641 Sagittarii
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Tanabe Kenji , Kiyota Seiichiro , Monard Berto , Stubbings Rod , Nelson Peter , Richards Tom , Bailyn Charles , Santallo Roland
Published: March 2014

We report on unprecedented short-term variations detected in the optical flux from the black hole binary system, V4641 Sgr. The amplitudes of the optical fluctuations were larger at longer time scales, and surprisingly reached $ \sim 60\%$ around a period of $ \sim10 \,\mathrm{min}$. The power spectra of the fluctuations are characterized by a power law ($ \propto f^{-\alpha},\; \alpha \sim-1.7$). It is the first case for black hole binaries that the optical emission was revealed to show short-term and large-amplitude variations given by such a power spectrum. The optical emission from black hole binaries is generally dominated by the emission from the outer portion of an accretion disc. The rapid optical fluctuations, however, indicate that the emission from an inner accretion region significantly contributes to the optical flux. In this case, cyclo-synchrotron emission associated with various scales of magnetic flares is the most promising mechanism for the violently variable optical emission.

PASJ: Publ. Astron. Soc. Japan 54, L79-L82, 2002 October 25 (C) 2002. Astronomical Society of Japan
Time-Resolved Photometry of GK Persei during the 1996 Outburst
Authors: Nogami Daisaku , Kato Taichi , Baba Hajime
Published: March 2014

GK Per is a unique cataclysmic variable star which has shown a nova explosion as well as dwarf nova-type outbursts, and has an intermediate-polar nature. We carried out $V$-band time-resolved photometry and $B$-band monitoring during the 1996 outburst. This outburst lasted for about 60 d, and was divided into three parts: a slow-rise branch for 35 d, a gradual-decay branch with a decay rate of $20.0 \,\mathrm{d} \,\mathrm{mag}^{-1}$ for $\sim 16 \,\mathrm{d}$, and a rapid-decline branch with a rate of $5.6 \,\mathrm{d} \,\mathrm{mag}^{-1}$ for $\sim 10 \,\mathrm{d}$. The $B-V$ color became bluest ($B-V \sim 0.18$) at about 10 d before the outburst maximum, which supports an idea that the outburst in GK Per is of the inside-out type. The spin pulse, 440-s quasi periodic oscillations (QPOs), and $\sim 5000$-s QPOs were detected in our light curve, as previously seen in X-ray and optical observations. In addition, we report on the discovery of an $\sim 300$-s periodicity, which is shorter than the spin period.
Interferometric Observations of Formaldehyde in the Protoplanetary Disk around LkCa 15
Authors: Aikawa Yuri , Momose Munetake , Thi Wing-Fai , van Zadelhoff Gerd-Jan , Qi Chunhua , Blake Geoffrey A. , van Dishoeck Ewine F.
Published: March 2014

Emission from the $2_{12} \hbox{-} 1_{11}$ line of $\mathrm{H}_2\mathrm{CO}$ has been detected and marginally resolved toward LkCa 15 by the Nobeyama Millimeter Array. The column density of $\mathrm{H}_2\mathrm{CO}$ is higher than that observed in DM Tau and than predicted by theoretical models of disk chemistry; also, the line-intensity profile is less centrally peaked than that for CO. A similar behavior is observed in other organic gaseous molecules in the LkCa 15 disk.
Silhouette of a Dressed Black Hole
Authors: Fukue Jun
Published: March 2014

In the case of the traditional standard disk with an inner radius of $3 \,r_{\mathrm{g}}$ (three Schwarzschild radii) around the Schwarzschild black hole, there appears to be a dark central shadow with a radius of about $3 \,r_{\mathrm{g}}$. In the case of a disk extending down to $1 \,r_{\mathrm{g}}$, on the other hand, we found that the radius of the dark shadow is about $2 \,r_{\mathrm{g}}$. These shadow sizes are different from that obtained by Falcke et al. (2000, AAA 073.155.002), where the shadow radius is about $2.6 \,r_{\mathrm{g}}$. This is because they considered an optically-thin spherical envelope, while we assumed an optically-thick luminous disk. In addition, we found that in an edge-on view the central shadow becomes a semicircle due to the projection effect. Such a silhouette of a dressed black hole throws light on the space-time structure of the hole as well as the type of surrounding disk.
Review of Discrete X-Ray Sources in the Small Magellanic Cloud: Summary of the ASCA Results and Implication on the Recent Star-Forming Activity
Authors: Yokogawa Jun , Imanishi Kensuke , Tsujimoto Masahiro , Koyama Katsuji , Nishiuchi Mamiko
Published: March 2014

We made 22 observations on the Small Magellanic Cloud (SMC) and covered full regions of the main body and the eastern wing by the end of the ASCA mission. We detected 106 discrete sources with a criterion of $\mathrm{S/N} \gt 5$$\mathrm{S/N} \gt 5$ and performed systematic analyses on all of the sources. We determined the source positions with an $\sim {40{}^{\mathrm {\prime \prime }}}$ error radius (90% confidence) for sources detected in the central ${20{}^{\mathrm {\prime }}}$ radius of the GIS. We detected coherent pulsations from 17 sources. Among them, eight were newly discovered during this study. We classified most of these pulsars as X-ray binary pulsars (XBPs) based on their properties, such as the flux variability and the existence of an optical counterpart. We detected X-ray emission from eight supernova remnants (SNRs). Among them, five SNRs showed emission lines in their spectra, hence we regarded the five as thermal SNRs. We found that XBPs and thermal SNRs in the SMC can be clearly separated by their spectral hardness ratio. Applying this empirical law to faint (thus unclassified) sources, we found 19 XBP candidates and four thermal SNR candidates. We also found several tens of candidates for active galactic nuclei, both from the hardness ratio and the $\log N \hbox{--}\log S$ relation of extragalactic sources. Based on these ASCA results and further information from ROSAT, SAX, RXTE, CGRO, Chandra, and XMM-Newton, we compiled comprehensive catalogues of discrete X-ray sources in the Small Magellanic Cloud. Using the catalogues, we derived the spatial distributions of XBPs and SNRs. XBPs and SNRs were found to be concentrated in the main body and eastern wing, which resembles the distribution of young stars with ages of $\sim 2 \times 10^7 \,\mathrm{yr}$. By comparing the source populations in the SMC and our Galaxy, we suggest that the star-forming rate (per unit mass) in the SMC was much higher than the Galaxy $\sim 10^7 \,\mathrm{yr}$ ago. We also discuss the recent change of the star-forming rate in the SMC.
SiO Maser Survey of Cold IRAS Sources
Authors: Nakashima Jun-ichi , Deguchi Shuji
Published: March 2014

We present the results of observations of cold IRAS sources in the Galactic disk area, $-10^{\circ} < l < 100^{\circ}$ and $\vert b\vert < 5^{\circ}$, in the SiO $J = 1\hbox{--}0$, $v = 1$ and 2 maser lines. SiO masers were detected in 51 out of 143 observed sources; 45 were new detections in SiO masers. The selected IRAS sources were objects with dust temperatures of between 160 and 280 K. According to a confirmation using 2MASS near-infrared images, a majority of the sample are AGB or post-AGB stars, although dense cores in the star-forming regions (or dusty H ii regions) are involved in part of the sample. Among new detections, two were candidates for post-AGB stars: IRAS 18450$-$0148 (W43 A), and 19312$+$1950. We found that the intensity ratios of the SiO $J = 1\hbox{--}0$, $v = 2$ to the $v = 1$ line of the objects clearly correlate with those IRAS colors. The detection rates of SiO masers tend to increase toward the Galactic center as well as the cases of previous SiO maser surveys of typical AGB stars. No strong associations of the objects to the spiral arms were found. The radial-velocity dispersion of the present sample is comparable with the dispersion of the SiO maser sample of typical AGB stars. These facts suggest that the present sample of cold IRAS sources with SiO masers has a kinematic property very similar to that of typical AGB stars.
Observational Evidence for a High-Energy Compton Cloud in GRO J1655-40 under a High Accretion Rate
Authors: Kobayashi Yoshihito , Kubota Aya , Nakazawa Kazuhiro , Takahashi Tadayuki , Makishima Kazuo
Published: March 2014

Observational results on GRO J1655$-$40 are reported, based on the X-ray spectra obtained with the PCA and the HEXTE on-board RXTE during its 1996–1997 outburst. By referring to the 40–150 keV X-ray luminosity, $L_{40 \hbox{--} 150}$, six typical spectra were selected and analyzed. When $L_{40 \hbox{--} 150}$ is sufficiently below $\sim 5 \times 10^{36} \mathrm{erg} \,\mathrm{s}^{-1}$ (assuming a distance of 3.2 kpc and an isotropic emission), the 3–150 keV PCA/HEXTE spectra are well described by a standard spectral model consisting of an optically-thick disk spectrum and a power-law tail. When $L_{40 \hbox{--} 150}$ exceeds $5 \times 10^{36} \,\mathrm{erg} \,\mathrm{s}^{-1}$, the standard model fails to reproduce the joint spectrum, due to a mild turn-over in the HEXTE spectrum. Successful fits are recovered when the power-law component is replaced by a broken power-law model with the break energy at $\sim 40 \,\mathrm{keV}$, or by an exponentially cutoff power-law model with the cutoff energy at 190–300 keV. The fits are further improved by employing a thermal Comptonization component, wherein the electron temperature and optical depth of the Compton cloud are estimated to be 70–85 keV and 0.45–0.65, respectively. These results provide strong evidence for the existence of thermal high-energy electrons, and reconfirm the picture of strong disk Comptonization.
Evidence for Jet Collimation in SS 433 with the Chandra HETGS
Authors: Namiki Masaaki , Kawai Nobuyuki , Kotani Taro , Makishima Kazuo
Published: March 2014

High-resolution X-ray spectra of SS 433 obtained after a binary egress with the Chandra High Energy Transmission Grating Spectrometer (HETGS) were studied. Many Doppler-shifted X-ray emission lines from highly ionized elements were detected. The initial temperature of the jets is estimated to be 20 keV. The lines are found to generally be broader than the instrumental resolution. The widths of the Fe xxv$\mathrm{K}\alpha$ and Si xiii$\mathrm{K}\alpha$ lines correspond to velocity dispersions of $2100^{+600}_{-340} \,\mathrm{km} \,\mathrm{s}^{-1}$ and $840^{+180}_{-150} \,\mathrm{km} \,\mathrm{s}^{-1}$ respectively, in terms of Gaussian sigma. Neither the measured line widths nor their dependence on the atomic number can be explained by thermal broadening alone. Alternative explanations of the observed line widths are discussed, including in particular a progressive jet collimation along its axis.
Multi-Line Observations of Molecular Gas in the Central Region of the Low Star-Formation Efficiency “Starburst” Galaxy NGC 4527
Authors: Shibatsuka Toshihito , Matsushita Satoki , Kohno Kotaro , Kawabe Ryohei
Published: March 2014

We performed high-resolution CO($J = 2 \hbox{--} 1$), CO($J = 1 \hbox{--} 0$), HCN($J = 1 \hbox{--} 0$), $\mathrm{HCO}^{+}$($J = 1 \hbox{--} 0$), and 3 mm continuum observations of the low star formation efficiency (SFE) “starburst” galaxy NGC 4527 with the Nobeyama Millimeter Array. From CO($J = 1 \hbox{--} 0$) observations, we found two offset ridges with non-circular motion and a central gas concentration. The distribution and kinematics of NGC 4527 are very similar to those of barred spiral galaxies. The distribution of CO($J = 2 \hbox{--} 1$) emission resembles the features of the concentrated component of CO($J = 1 \hbox{--} 0$). HCN($J = 1 \hbox{--} 0$) and $\mathrm{HCO}^{+}$($J = 1 \hbox{--} 0$) emissions concentrated toward the center have also been detected. The total mass of molecular gas detected in the central $r < {30{}^{\mathrm {\prime \prime }}}$ is $2.5 \times 10^9 \,{{{M}_{\odot}}}$. The $\mathrm{HCN}\,(J = 1 \hbox{--} 0) / \mathrm{CO}\,(J = 1 \hbox{--} 0)$ integrated intensity ratio of $0.075 \pm 0.008$ in the central $r \lesssim {3{}^{\mathrm {\prime \prime }}} \hbox{--} {4{}^{\mathrm {\prime \prime }}}$ region of NGC 4527 could suggest that the fraction of dense molecular gas to the total molecular gas is small compared with those of prototypical starburst galaxies, such as NGC 253. This suggests that the small dense gas fraction is responsible for the low SFE in the center of NGC 4527, though this interpretation could depend on aperture sizes of the observations. The ratio of the dynamical mass to molecular gas mass is 13% within the central region ($r < 500 \,\mathrm{pc}$). This suggests that molecular gas within the $r < 500 \,\mathrm{pc}$ region could be in a state of gravitational instability. The low SFE, the small dense gas fraction, and the large amount of gravitationally unstable molecular gas can be explained if NGC 4527 is in the very early phase of starburst phenomena or a pre-starburst phase, and the formation of dense molecular gas will begin and the SFE will increase within a short time scale.
Application of a Self-Organizing State Space Model to the Leonid Meteor Storm in 2001
Authors: Takeuchi Tsutomu T. , Shiki Shigetomo , Miyamoto Daisuke , Fujiwara Hideaki , Kitazume Jun , Utsumi Yousuke
Published: March 2014

The Leonids show meteor storms with a period of 33 years, and are known as one of the most active meteor showers. It has recently shown a meteor stream consisting of several narrow dust trails made by meteoroids ejected from a parent comet. Hence, an analysis of the temporal behavior of the meteor flux is important to study the structure of the trails. However, statistical inference for the count data is not an easy task, because of its Poisson characteristics. We carried out a wide-field video observation of the Leonid meteor storm in 2001. We formulated a state-of-the-art statistical analysis, which is called a self-organizing state space model, to infer the true behavior of the dust density of the trails properly from the meteor count data. From this analysis, we found that the trails have a fairly smooth spatial structure, with small and dense clumps that cause a temporal burst of meteor flux. We also proved that the time behavior (trend) of the fluxes of bright meteors and that of faint meteors are significantly different. In addition we comment on some other application of the self-organizing state space model in fields related to astronomy and astrophysics.
Discovery of a Short Plateau Phase in the Early Evolution of a Gamma-Ray Burst Afterglow
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Yamaoka Hitoshi
Published: March 2014

We report on optical observations during the first hour of the gamma-ray burst (GRB) afterglow of GRB 021004. Our observations revealed the existence of a short plateau phase, in which the afterglow remained at almost constant brightness, before an ordinary rapid-fading phase. This plateau phase lasted for about 2 hours from 0.024 to 0.10 d after the burst, which corresponds to a missing blank of the early afterglow light curve of GRB 990123. We propose that the plateau phase can be interpreted as being the natural evolution of synchrotron emission from the forward shock region of a blast wave. The time when the typical frequency of the synchrotron emission passes through the optical range has been predicted to be about 0.1 d after the burst, which is consistent with the observed light curve. Our scenario hence implies that the observed feature in GRB 021004 is a common nature of GRB afterglows.
Superhumps in a Rarely Outbursting SU UMa-Type Dwarf Nova, HO Delphini
Authors: Kato Taichi , Nogami Daisaku , Moilanen Marko , Yamaoka Hitoshi
Published: March 2014

We observed the 1994, 1996, and 2001 outbursts of HO Del. From the detection of secure superhumps, HO Del is confirmed to be an SU UMa-type dwarf nova with a superhump period of 0.06453(6)d. Based on recent observations and past records, the outbursts of HO Del are found to be relatively rare, with the shortest intervals of superoutbursts being $\sim 740 \,\mathrm{d}$. Among SU UMa-type dwarf novae with similar outburst intervals, the outburst amplitude ($\sim 5.0 \,\mathrm{mag}$) is unusually small. HO Del showed a rather rapid decay of the superhump amplitudes, and no regrowth of the amplitudes during the later stage, in contrast to the commonly observed behavior in SU UMa-type dwarf novae with long outburst intervals. We positively identified HO Del with a ROSAT X-ray source, and obtained a relatively large X-ray luminosity of $10^{31.1 \pm 0.2} \,\mathrm{erg} \,\mathrm{s}^{-1}$. We also performed a literature survey of SU UMa-type dwarf novae and presented a new set of basic statistics. The SU UMa-type dwarf novae with a brightening trend or with a regrowth of superhumps near the termination of a superoutburst are found to be rather tightly confined in a small region on the (superhump period–supercycle length) plane. These features may provide a better observational distinction for the previously claimed subgroup of dwarf novae (Tremendous Outburst Amplitude Dwarf Novae).
43 GHz SiO Masers and Astrometry with VERA in the Galactic Center
Authors: Sjouwerman Loránt O. , Messineo Maria , Habing Harm J.
Published: March 2014

We present Very Large Array (VLA) observations of 43 GHz SiO ($J = 1 \hbox{--} 0, v=2$ and $v=1$) maser emission in a sub-sample of late-type stars in the Inner Galaxy selected on their relatively strong ($ \gt 0.5 \,\mathrm{Jy}$) 86 GHz SiO masers, and located within ${2\rlap {.}{}^{\mathrm {\circ }}5}$ of the galactic center. Furthermore we combine these results with a summary of previous surveys for 43 GHz SiO masers in the galactic center and comment on their use as calibrators for the Japanese “VLBI Exploration of Radio Astrometry” (VERA) network, which is intended to perform sub-milli-arcsecond astrometry in the Galaxy and the galactic center.
SiO Maser Survey of the Large-Amplitude Variables in the Galactic Center
Authors: Deguchi Shuji , Imai Hiroshi , Fujii Takahiro , Glass Ian S. , Ita Yoshifusa , Izumiura Hideyuki , Kameya Osamu , Miyazaki Atsushi , Nakada Yoshikazu , Nakashima Jun-ichi
Published: March 2014

We have surveyed $\sim 400$ known large-amplitude variables within $15'$ of the galactic center in the SiO ${J = 1 \hbox{--} 0} {v = 1}$ and 2 maser lines at 43 GHz, resulting in 180 detections. SiO lines were detected from 16 other sources located within $20''$ of the program objects. The detection rate of 48% is comparable to that in bulge IRAS surveys. Among the detections, five stars have radial velocities greater than $200 \,\mathrm{km} \,\mathrm{s}^{-1}$. The detection rate increases steeply with the period of light variation, particularly for stars with $P \gt 500 \,\mathrm{d} P \gt 500 \,\mathrm{d}$, where it exceeds 80%. At a given period, the SiO detection rate is approximately three-times that for OH. These facts suggest that the large-amplitude variables in the Nuclear Disk region are AGB stars similar in their overall properties to the inner and outer bulge IRAS/SiO sources. From the set of radial velocity data, the mass distribution within 30 pc of the galactic center was derived based on the collisionless Boltzmann equation integrated along the line of sight. The mass is about $6.5\,(\pm 0.7) \times 10^7 \,{{{M}_{\odot}}}$ and the mass of the central black hole is $2.7\,(\pm 1.3) \times 10^6 \,{{{M}_{\odot}}}$. From the line-of-sight velocity of each star and its potential energy we conclude that the five high-velocity stars come from galactocentric distances as far as 300 pc. A high-velocity subsample of stars with negative radial velocities exhibits a tendency to have brighter $K$ magnitudes than a subsample with positive velocities. The origin of these stars is discussed.
Energetics of a Black Hole-Accretion Disk System with Magnetic Connection: Limit of Low Accretion Rate
Authors: Li Li-Xin
Published: March 2014

We consider the energetics of a black hole-accretion disk system with magnetic connection: a Keplerian disk is connected to a Kerr black hole by a large-scale magnetic field. We assume that 1) the magnetic field is locked to the inner boundary of the disk and corotates with it, and 2) the accretion rate is low, but the accretion from the disk can still provide a sufficient amount of cold plasma particles in the transition region so that the magnetohydrodynamics approximation is valid. By finding solutions that smoothly pass the fast critical point near the equatorial plane, we find that a system with a fast rotating black hole and that with a slow rotating black hole behave very differently. For a black hole with $a \gt a_\mathrm{cr} \equiv 0.3594 \,M a > a_\mathrm{cr} \equiv 0.3594 \,M$, where $M$ is the mass and $a$ is the specific angular momentum of the black hole, the spinning energy of the black hole is efficiently extracted and transported to the disk, thus increasing the radiation efficiency of the disk by orders of magnitude. For a black hole with $0 \leq a < a_\mathrm{cr}$, the inner region of the disk is disrupted by the magnetic field and the inner boundary moves out to a radius where the angular velocity of the disk is equal to the spinning angular velocity of the black hole. As a result, the disk may have an extremely low radiation efficiency if $0\leq a/M \ll 1$.
Units of Time in Ancient China and Japan
Authors: Sôma Mitsuru , Kawabata Kin-aki , Tanikawa Kiyotaka
Published: March 2014

The time systems employed in ancient China and Japan are discussed. It is well known that both in ancient China and Japan 1 day was divided into 12 double hours, and the first double hour began at 23 hr local time. However, it is confirmed in this paper that in the Chinese Song dynasty the first double hour began at 0 hr local time. One day was also divided into 100 equal parts, called ke, and ke was subdivided by a time unit called fen. The number of fen in 1 ke varied from dynasty to dynasty. These numbers were clarified by analyzing the tables of daytime duration given in the official Chinese chronicles. In ancient Japan, the time units ke and fen were also used, but the lengths of both of them varied depending on the era. It has been found that all of the daytime and nighttime, the times of sunrise and sunset, and the lengths of shadows given in the official Chinese chronicles refer to a particular latitude of about ${34\rlap {.}{}^{\mathrm {\circ }}5}$, and that the Japanese system adopted this Chinese tradition. Symmetry of the data in tables with respect to certain dates was also investigated in detail in order to examine how the dates of 24 qis were determined.
Precise Differential Analysis of Stellar Metallicities: Application to Solar Analogs Including 16 Cyg A and B
Authors: Takeda Yoichi
Published: March 2014

A method is presented for very accurately establishing the differences of the atmospheric parameters (the effective temperature, the surface gravity, the microturbulent velocity, and the Fe abundance) between two similar stars by using the equivalent widths of Fe I and Fe II lines, which is a variant of the numerical solution-search approach developed by Takeda et al. (2002, PASJ, 54, 451), while being inspired by the spirit of the orthodox “differential curve-of-growth” procedure. By applying this technique to eight selected stars similar to the Sun [HD 20630, 76151, 134987, 181655, 186408 (16 Cyg A), 186427 (16 Cyg B), 195019, and 217014] along with the Sun itself, the parameter differences between any pairs of these stars could be successfully determined to precisions of $\sim 10 \,\mathrm{K}$ (in $\Delta T_{\mathrm{eff}}$), $\sim 0.02 \,\mathrm{dex}$ (in $\Delta\log g$), $\sim 0.02 \,\mathrm{km} \,\mathrm{s}^{-1}$ (in $\Delta v_{\mathrm{t}}$), and $\sim 0.01 \,\mathrm{dex}$ (in $\Delta A_{\mathrm{Fe}}$). Regarding 16 Cyg A and B, a well-known “solar twin” system where a planet has been detected only in B, the metallicities of these two components were concluded to be essentially the same to a level of $\lesssim 0.01 \,\mathrm{dex}$.
The Schmidt Law at High Molecular Densities
Authors: Komugi Shinya , Sofue Yoshiaki , Nakanishi Hiroyuki , Onodera Sachiko , Egusa Fumi
Published: March 2014

We combined $\mathrm{H}\alpha$ and recent high-resolution ${{12\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) data to consider the quantitative relation between the gas mass and the star-formation rate, or the so-called Schmidt law in nearby spiral galaxies at regions of high molecular density. The relation between the gas quantity and the star-formation rate has not been previously studied for high-density regions, but using high-resolution CO data obtained at the Nobeyama Millimeter Array, we found that the Schmidt law is valid at densities as high as $10^3 \,{{{M}_{\odot}}} \,\mathrm{pc}^{-2}$ for sample spiral galaxies, which is an order of magnitude denser than what has been known to be the maximum density at which the empirical law holds for non-starburst galaxies. Furthermore, we obtained a Schmidt law index of $N = 1.33 \pm 0.09$ and a roughly constant star-formation efficiency over the entire disk, even within several hundred parsecs of the nucleus. These results imply that the physics of star formation does not change in the central regions of spiral galaxies. Comparisons with starburst galaxies are also given. We find a possible discontinuity in the Schmidt law between normal and starburst galaxies.
XMM-Newton Observation of IC 310 in the Outer Region of the Perseus Cluster of Galaxies
Authors: Sato Kosuke , Furusho Tae , Yamasaki Noriko Y. , Ishida Manabu , Matsushita Kyoko , Ohashi Takaya
Published: March 2014

We present results from an XMM-Newton observation of the head-tail radio galaxy IC 310 located in the southwest region of the Perseus cluster. The spectrum is well fitted by an absorbed power-law model with a photon index of $2.50 \pm 0.02$ without significant absorption excess. The X-ray image shows a point-like emission at IC 310 without any sign of a structure correlated with the radio halo tail. The temperature of the intracluster medium surrounding IC 310 declines as a function of distance from the cluster center, from $kT \sim 6 \,\mathrm{keV}$ in the northeast corner of the field of view to about 3 keV in the southwest region. Although we do not find any sharp edges in the surface brightness profile, a brightness excess of about 20% over a smooth $\beta$ model is seen. The temperature also rises by about 10% in the same region. This indicates that the IC 310 region is a subcluster probably infalling into the Perseus cluster, and the gas in front of IC 310 towards the Perseus cluster is likely to be compressed by the large-scale motion, which supports the view that the IC 310 system is undergoing a merger.
Discovery of a Strongly Lensed Galaxy at z=3.9 behind a z=0.83 Galaxy Cluster
Authors: Umetsu Keiichi , Tanaka Masayuki , Kodama Tadayuki , Tanaka Ichi , Futamase Toshifumi , Kashikawa Nobunari , Hoshi Takako
Published: March 2014

We report on the discovery and spectroscopic confirmation of three gravitationally-lensed images of a galaxy at $z=3.9$ in the background of a distant, rich cluster of galaxies at $z=0.83$, on the basis of observations with Faint Object Camera And Spectrograph on the Subaru telescope. We construct a simple lens model of the cluster mass distribution based on Jee et al.’s weak lensing mass estimates from deep, high-resolution images by Advanced Camera for Surveys on the Hubble Space Telescope. The lens model can account simultaneously for the observed image configuration and the flux ratio of the closer pair located close to the critical curve. The parities of the three images are also consistent with the lensing hypothesis. Since this galaxy is apparently bright ($i'_{\mathrm{AB}} \sim 23.7$) for its redshift due to magnification, it serves as a good high-redshift target on which we can make extensive and detailed studies based on multi-wavelength imaging and spectroscopy.