bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Variations of XTE J1859+226 during the 1999 Outburst
Authors: Uemura Makoto , Kato Taichi , Pavlenko Elena , Shugarov Sergei , Mitskevich Marina , Fried Robert E. , Sano Yasuo
Published: March 2014

We report on our optical photometric observations of a black hole X-ray transient, XTE J1859$+$226 ($=$V406 Vul). We detected an optical reflare associated with an X-ray reflare about 50 d after the outburst maximum. The X-ray delay of the reflare was shorter than 2.3 d. We detected coherent modulations having a period of $0.38385 \pm 0.00073 \,\mathrm{d}$. The modulation appeared within 7 d after the outburst maximum. We propose two obvious interpretations for the nature of the modulations, that is, superhumps or orbital-period variations caused by an irradiated secondary star or an outer disk. The asymmetric profile of the modulations suggests the superhump scenario. The early appearance of superhumps indicates that the tidal dissipation had already grown before the reflare. The growing tidal dissipation is hence less likely to induce the reflare. In conjunction with the short X-ray delay of the reflare, the reflare may be triggered by the X-ray irradiation onto an outer cold disk. The appearance of humps may be earlier than the eccentricity growth time expected from the tidal instability model. It may imply a mass ratio larger than what could be inferred from the reported orbital period.
Photometric Observations of an SU UMa-type Dwarf Nova, VW Coronae Borealis, during Outbursts
Authors: Nogami Daisaku , Uemura Makoto , Ishioka Ryoko , Kato Taichi , Pietz Jochen
Published: March 2014

We report on photometric observations of an SU UMa-type dwarf nova, VW CrB, during two superoutbursts in 2001 and 2003 and a normal outburst in 2003. Superhumps with a period of 0.07287(1) d were observed during the 2003 superoutburst. The change rate of the superhump period was positive. During a normal outburst, there is some hint of modulation up to a 0.2-mag amplitude. However, no periodicity was found. The recurrence cycles of the normal outburst and the superoutburst, and the distance were estimated to be $\ge 50 \,\mathrm{d}$, $270 \sim 500 \,\mathrm{d}$, and $690^{+230}_{-170} \,\mathrm{pc}$, respectively. These recurrence cycles are the usual values for an SU UMa-type dwarf nova having this superhump period. The superhump period of VW CrB was the longest among those of SU UMa stars with positive derivatives of the superhump period. The coverage of our observations was, however, not sufficient, and the variation of the $P_\mathrm{SH}$ change rate of VW CrB is still unknown. A superhump regrowth and a brightening were seen near the end of the plateau phase. Measuring the deviation of the start timings of the brightening and the superhump regrowth ($ \gt 2$ days in VW CrB) will be a key to reveal the mechanism of these phenomena.
Optical Variability of the Afterglow of GRB 030329
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Yamaoka Hitoshi , Monard Berto , Nogami Daisaku , Maehara Hiroyuki , Sugie Atsushi , Takahashi Susumu
Published: March 2014

We report on the optical light curve of the afterglow of GRB 030329. Our observation combined with publicly available data sets revealed that the light curve was rich in unexpectedly complicated structures throughout $\sim 6$ days after the burst. Our early observation indicates that the light curve can be described by a single power-law model with bumps until a supernova component became dominant. The bumps superimposed on a fading trend had roughly constant amplitudes and colors. The long-lived, large-amplitude variations indicate that additional energy was supplied for the shock region. The refreshed shock scenario is most plausible. The observed slopes of the bumps during early times, however, contradict the prediction of this model.
A New SU UMa-Type Dwarf Nova, QW Serpentis (= TmzV46)
Authors: Nogami Daisaku , Uemura Makoto , Ishioka Ryoko , Iwamatsu Hidetoshi , Kato Taichi , Pavlenko Elena P. , Baklanov Alex , NovÁk Rudolf , Kiyota Seiichiro , Tanabe Kenji , Masi Gianluca , Cook Lewis M. , Morikawa Koichi , Schmeer Patrick
Published: March 2014

We report on the results of the QW Ser campaign, which has been continued from 2000 to 2003 by the VSNET collaboration team. Four long outbursts and many short ones were caught during this period. Our intensive photometric observations revealed superhumps with a period of $0.07700(\pm 0.00004) \,\mathrm{d}$ during all four superoutbursts, proving the SU UMa nature of this star. The recurrence cycles of the normal outbursts and the superoutbursts were measured to be $\sim 50$ days and $240(\pm 30)$ days, respectively. The change rate of the superhump period was $-5.8 \times 10^{-5}$. The distance and the X-ray luminosity in the range of 0.5–2.4 keV are estimated to be $380(\pm60) \,\mathrm{pc}$ and $\log L_\mathrm{X} = 31.0 \pm 0.1 \,\mathrm{erg} \,\mathrm{s}^{-1}$. These properties have typical values for an SU UMa-type dwarf nova with this superhump period.
Forty Years of Spectroscopic Stellar Astrophysics in Japan
Authors: Sadakane Kozo , Hirata Ryuko , Tsuji Takashi
Published: March 2014

The development of Japanese spectroscopic stellar astrophysics in the recent 40 years is reviewed from an observational point of view. In this article, the research activities are provisionally divided into four fields: hot stars, hot emission-line (Be) stars, cool stars, and other stars. Historical developments of the observational facilities at Okayama Astrophysical Observatory (spectrographs and detectors) are also summarized in connection with the progress in scientific research activities.
Light-Curve and Period Changes in the W UMa-Type System TY Bootis
Authors: Li Lifang , Han Zhanwen , Zhang Fenghui
Published: March 2014

A detailed study of the period and the light curve of the eclipsing binary TY Bootis is presented. Based on a study of the $(\mathrm{O}-\mathrm{C})$ curve, we have found that two periodical variations superimpose on a continuous increase ($dP/dt = 6.283 \times 10^{-8} \,\mathrm{d} \,\mathrm{yr}^{-1}$) in its period. We compared light curves obtained by other groups, and found that the light curve of the system has changed considerably. We analyzed the physical mechanisms that underlie the variation in the period and light curve of the system, and obtained some new conclusions. The continuous increase of its orbital period is probably caused by mass transfer from the secondary to the primary, rather than an expansion of the primary due to its dynamical instability. Also, the two periodical components are probably caused by two different physical mechanisms, i.e., the light-time effect is one of the possible mechanisms, which might cause a periodical component with a longer timescale (31.5 yr), and the magnetic activity cycle is the other one, which might underlie the other periodical component with a shorter timescale (11.76 yr). The long-term variation in the light curve of the system is likely to be caused by a decrease in the light level of the primary due to starspot(s) on the primary or an expansion of the primary. Finally, the trends in the evolution of the system are discussed according to a theory of W UMa systems.
V1647 Orionis (IRAS 05436$-$0007): A New Look at McNeil’s Nebula
Authors: Ojha Devendra , Kusakabe Nobuhiko , Tamura Motohide , Nakajima Yasushi , Fukagawa Misato , Sugitani Koji , Baba Daisuke , Kato Daisuke , Kurita Mikio , Nagashima Chie , Nagayama Takahiro , Nagata Tetsuya , Sato Shuji
Published: March 2014

We present a study of the newly discovered McNeil’s nebula in Orion using simultaneous observations of the $JHK_{\mathrm{s}}$-bands with the near-infrared (NIR) camera SIRIUS on the IRSF 1.4m telescope. The cometary infrared nebula is clearly seen extending toward both north and south from the NIR source (V1647 Orionis), which illuminates McNeil’s nebula. The compact nebula has an apparent diameter of about $70 {}^{\prime \prime }$. The nebula is blue (bright in $J$) and has a cavity structure with two rims extending toward the north-east and the north-west. The north-east rim is brighter and sharp, while the north-west rim is diffuse. The north-east rim can be traced out to $\sim 40 {{}^{\prime \prime }}$ from the location of the NIR source. In contrast, no cavity structure can be seen toward the south, although the diffuse nebula is extended out to $\sim 20 {{}^{\prime \prime }}$. New NIR photometric data show a significant variation in the magnitudes ($\gt 0.15 \,\mathrm{mag} > 0.15 \,\mathrm{mag}$) of the source of McNeil’s nebula within a period of one week, which is possibly under the phase of eruptive variables, like FUors or EXors.
Pre-Collimator of the Astro-E2 X-Ray Telescopes for Stray-Light Reduction
Authors: Mori Hideyuki , Iizuka Ryo , Shibata Ryo , Yoshito Haba , Hayakawa Akira , Hayashi Atsushi , Inoue Chiaki , Inoue Hirohiko , Ishida Manabu , Itoh Akiharu , Itoh Kei , Kunieda Hideyo , Maeda Yoshitomo , Misaki Kazutami , Naitou Masataka , Okada Shunsaku , Shimizu Tomoo , Yokoyama Yushi
Published: March 2014

We present the design and fabrication of the pre-collimator for the X-ray telescope onboard the X-ray astronomy satellite Astro-E2, and its effect on stray-light reduction. The pre-collimator was designed to efficiently reduce secondary reflection, which is the brightest component of stray light, giving rise to a ghost image in the field of view of the focal-plane detector. With the pre-collimator, composed of blades with an effective height of 30 mm, we confirmed from X-ray measurements that the intensity of the secondary reflection is reduced by roughly a few orders of magnitude on average in the off-axis angle range of $20' \hbox{--} 70'$. We also confirmed that the loss of the on-axis effective area due to installation of the pre-collimator is only $0.5 \pm 0.2\%$. The field of view becomes narrower, but the reduction factor amounts only to 8%. Ray-tracing simulations of in-flight observations also demonstrate that introduction of the pre-collimator is expected to be highly significant for improving data quality, due to a reduction of secondary reflection.
SiO Maser Sources toward Globular Clusters
Authors: Matsunaga Noriyuki , Deguchi Shuji , Ita Yoshifusa , TanabÉ Toshihiko , Nakada Yoshikazu
Published: March 2014

We report on the detection of SiO masers in Asymptotic Giant Branch variables toward bulge/disk globular clusters. In five out of six cases, the radial velocities are compatible with the optically measured radial velocities of globular clusters in the assessed uncertainty. Two sources, toward Terzan 5 and Terzan 12, lie very close to the cluster centers. The objects toward Pal 6 and Terzan 12 have luminosities appropriate to the AGB tip in globular clusters, while those toward NGC 6171, Pal 10, and Terzan 5 are brighter than expected. It is suggested that the latter three may have evolved from merged binaries, offering a test for binary-evolution scenarios in globular clusters, if the membership is approved.
The Intermediate-Band Dropout Method: A New Method to Search for High-Redshift Galaxies
Authors: Shioya Yasuhiro , Taniguchi Yoshiaki , Ajiki Masaru , Nagao Tohru , Murayama Takashi , Sasaki Shunji , Sumiya Ryoko , Hatakeyama Yuichiro
Published: March 2014

We propose a new method to search for high-redshift galaxies that is based on an intermediate-band dropout technique rather than the usual broad-band dropout one. In this method, we use an intermediate-band filter whose central wavelength is longer than 7000 Å. This new method makes it possible to distinguish both very late-type stars, such as L and T dwarfs, and dusty galaxies at intermediate redshifts from real high-$z$ Lyman break galaxies. The reason for this is that such interlopers do not show strong intermediate-band depression, although they have very red broad-band colors that are indicative of Lyman break galaxies (LBGs). Applying our new method to imaging data sets obtained with Suprime-Cam on the Subaru Telescope, we found a new sample of Lyman break galaxies at $z \simeq 5$.
Time Variation of SiO Masers in VX Sagittarii over an Optically Quiescent Phase
Authors: Kamohara Ryuichi , Deguchi Shuji , Miyoshi Makoto , Shen Zhi-Qiang
Published: March 2014

The time variation of SiO masers in a semi-regular variable, VX Sgr, was investigated in the period between 1994 and 2004 when the optical light curve exhibited an $\sim 6$-yr quiescent phase intercepting a regularly pulsating era. The quiescent period occurred with a delay of several years after a decrease in the SiO maser flux. VLBA observations of SiO masers made during this period showed no drastic spatial variation except for emission features being shifted from south-west to north-east. The SiO maser flux decrease, and a succeeding optical quiescent phase, may indicate that the stellar mass-loss rate diminished over a few years around 1994. A SiO maser flare occurring in 1999 may be a reminiscence of a final gas blow, which resulted in the optically quiescent period.
Momentum Conservation and Mode Classification of the Dipolar Oscillations of Stars
Authors: Takata Masao
Published: March 2014

Despite their apparent simplicity, the dipole modes of stellar oscillations are theoretically less tractable than the other nonradial modes. This is because neglecting the Eulerian perturbation to the gravitational potential (the Cowling approximation), which greatly simplifies the governing equations, is not always very accurate in the case of dipole modes. In this paper, we first derive an integral that is specific to dipole-mode oscillations. It is then shown that the fourth-order differential equation, which governs the nonradial adiabatic oscillations of stars, is reduced to a (linear) second-order equation in the dipole case without assuming the Cowling approximation. Based on this second-order equation, we discuss how to classify the adiabatic dipole modes theoretically. We specifically propose a scheme that allocates a unique index to each of the dipole modes.
Automatic Detection Algorithm for Small Moving Objects
Authors: Yanagisawa Toshifumi , Nakajima Atsushi , Kadota Ken-ichi , Kurosaki Hirohisa , Nakamura Tsuko , Yoshida Fumi , Dermawan Budi , Sato Yusuke
Published: March 2014

We have devised an automatic detection algorithm for unresolved moving objects, such as asteroids and comets. The algorithm uses many CCD images in order to detect very dark moving objects that are invisible on a single CCD image. We carried out a trial observation to investigate its usefulness, using a 35-cm telescope. By using the algorithm, we succeeded to detect asteroids down to about 21 mag. This algorithm will contribute significantly to searches for near-Earth objects and to solar-system astronomy.
A Dynamical Model for the Orbit of the Andromeda Galaxy M31 and the Origin of the Local Group of Galaxies
Authors: Sawa Takeyasu , Fujimoto Mitsuaki
Published: March 2014

We propose a new model for the origin and evolution of the Local Group of Galaxies (LGG) that naturally explains the formation of the Magellanic Clouds and their large orbital angular momenta around the Galaxy. The basic idea is that an off-center hydrodynamical collision occurred some 10 Gyr ago between the primordial Andromeda galaxy (M31) and a similar Galaxy, and compressed the halo gas to form the LGG dwarf galaxies, including the Magellanic Clouds. New-born dwarf galaxies can be expected to locate on the orbital plane of these two massive galaxies. We reexamined the two-dimensional sky distribution of the LGG members, and confirmed an early idea that they align along two similar great circles. The planes of these circles are approximately normal to the line joining the present position of the Sun and the galactic center. We made a distribution map of these objects, and found a well-defined plane of finite thickness. Thus we could determine the orbital elements of M31 relative to the Galaxy by reproducing the well-studied dynamics of the LMC and the SMC around the Galaxy. The expected proper motion of M31 is $(\mu_{l}, \mu_{b}) = (38\pm 16 \,\mu\mathrm{as} \,\mathrm{yr}^{-1},-49 \pm 5 \, \mu\mathrm{as} \,\mathrm{yr}^{-1})$.
An Ultrasoft Transient X-Ray Source in the Norma Region Discovered with Ginga
Authors: Yamauchi Shigeo
Published: March 2014

A new X-ray source was discovered in the Norma region with Ginga in 1988 April. The source position, derived from one-dimensional scan data, and its spectral properties are presented. The X-ray emission was dominant below $\sim 6 \,\mathrm{keV}$ and not found in other observations. Thus, it is thought to be an ultrasoft transient X-ray source. The X-ray spectrum, constructed by a scan fit technique, was well represented by either blackbody, thermal bremsstrahlung, power-law, or multicolor disk models. Although all of the spectral models were acceptable from a statistical point of view, the ultrasoft nature of the spectrum and the transient behavior suggest that this source is a candidate source of black hole binaries.
2003 Mars Report from Cooperative Observation Networks. II. After the Opposition
Authors: Nakakushi Takashi , Adachi Makoto , Iga Yuichi , Ikemura Toshihiko , Tokimasa Noritaka , Narumi Yasunori
Published: March 2014

This is the second report on Mars in 2003 by two networks for cooperative Mars observations in Japan: Nishi-Harima Astronomical Observatory Mars Cooperative Observation and Association of Lunar and Planetary Observers in Japan. This paper is a summary of 4145 data for 226 nights collected by the two networks during the second half of the last apparition from 2003 September 1 through 2004 June 22, corresponding to a period of $L_{\mathrm{s}} \sim 252 {{}^{\mathrm {\circ }}} \hbox{--} 51 {{}^{\mathrm {\circ }}}$ ($L_{\mathrm{s}}$ is the areocentric longitude of the Sun). During this period, many interesting phenomena were observed: (1) Albedo features did not show a large difference from the first half of the period. (2) Blue clearings due to the opposition effect and due to the cloud effect were, respectively, observed. (3) South polar cap (SPC) recession was usual. The recession rate in $\sim 210 {{}^{\mathrm {\circ }}} \hbox{--} 270 {{}^{\mathrm {\circ }}}\mathrm{W}$ increased and that in $\sim 30 {{}^{\mathrm {\circ }}} \hbox{--} 60 {{}^{\mathrm {\circ }}}\mathrm{W}$ decreased after $L_\mathrm{s} \sim 230 {{}^{\mathrm {\circ }}}$. (4) North polar hood (NPH) had a topography-synchronous wave structure with $\mbox{a wave number} = 1$ a wave number$= 1$. (5) Many water ice clouds (WICs) were observed. Some particular regions frequently had prominent WICs. Some of them were related to topography. (6) Dust storm “2003c” was detected on December 9 ($L_\mathrm{s} = 314 {{}^{\mathrm {\circ }}}$) in Chryse. The storm grew rapidly to a very large dimension in the southern mid-latitudes, encircling over half of Mars. Another dust core occurred on December 23 around Aurorae Sinus. (7) Another dust storm is suspected in $L_\mathrm{s} = 20 {{}^{\mathrm {\circ }}}$ over the south polar region.
Large-Scale Clustering of Sloan Digital Sky Survey Quasars: Impact of the Baryon Density and the Cosmological Constant
Authors: Yahata Kazuhiro , Suto Yasushi , Kayo Issha , Matsubara Takahiko , Connolly Andrew J. , Vanden Berk Daniel , Sheth Ravi , Szapudi István , Anderson Scott F. , Bahcall Neta , Brinkmann Jon , Csabai István , Fan Xiaohui , Loveday Jon , Szalay Alexander S. , York Donald
Published: March 2014

We report on the first result from the clustering analysis of SDSS quasars. We computed the two-point correlation function (2PCF) of SDSS quasars in redshift space at $8\,h^{-1} \,\mathrm{Mpc} < s < 500\,h^{-1} \,\mathrm{Mpc}$, with particular attention to its baryonic signature. Our sample consisted of 19986 quasars extracted from the SDSS Data Release 4. The redshift range of the sample is $0.72 \le z \le 2.24$ (the mean redshift is $\overline{z} = 1.46$) and the reddening-corrected $i$-band apparent magnitude range is $15.0 \le m_{i,\mathrm{rc}} \le 19.1$. Due to the relatively low number density of the quasar sample, the bump in the power spectrum due to the baryon density, $\Omega_{\mathrm{b}}$, is not clearly visible. The effect of the baryon density is, however, to distort the overall shape of the 2PCF. The degree of distortion makes it an interesting alternate measure of the baryonic signature. Assuming a scale-independent linear bias and a spatially flat universe, we combined the observed quasar 2PCF and the predicted matter 2PCF to put constraints on $\Omega_{\mathrm{b}}$ and $\Omega_{\Lambda}$ (the cosmological constant). Our result was fitted as $0.80-2.8\Omega_{\mathrm{b}} < \Omega_{\Lambda} < 0.90-1.4\Omega_{\mathrm{b}}$ at the $2 \,\sigma$ confidence level. The “mean” bias parameter of our quasar sample is $1.59 \,{\sigma_8}^{-1}$ (for $\Omega_{\mathrm{b}} = 0.04$ and $\Omega_{\Lambda} = 0.7$), where $\sigma_8$ is the top-hat mass fluctuation amplitude at $8\,h^{-1} \,\mathrm{Mpc}$. We also estimated the corresponding bias parameter of quasars at $z = 0, b_{\mathrm{QSO,Fry}}(0)$, assuming Fry’s bias evolution model. For $\Omega_{\mathrm{b}} = 0.04, \Omega_{\Lambda} = 0.73$, and $\Omega_{\mathrm{d}} = 0.23$, we found $b_{\mathrm{QSO,Fry}}(0) = 0.54 + 0.83 \,{\sigma_8}^{-1}$ which is valid for $0.6 < \sigma_8 < 1.0$.
High Angular Resolution Observations of the (J, K) = (1, 1), (2, 2), and (3, 3) Transitions of Ammonia in NGC 253
Authors: Takano Shuro , Hofner Peter , Winnewisser Gisbert , Nakai Naomasa , Kawaguchi Kentarou
Published: March 2014

The nearby starburst galaxy NGC 253 was mapped in the ammonia $(J, K) = (1, 1), (2, 2)$, and $(3, 3)$ lines in the 23 GHz region with the Very Large Array. The angular resolutions were about $4 {{}^{\prime \prime }} \times 3 {{}^{\prime \prime }}$. The distributions of the three lines were different from one another. The $(1, 1)$ and $(3, 3)$ lines were distributed along the bar mainly at the northeastern and southwestern regions from the center, but the $(2, 2)$ line is distributed mainly at two clumps in the southwestern region from the center. In addition, the $(1, 1)$ line showed absorption at the central region. The obtained rotational temperatures were $<15 \hbox{--} 28 \,\mathrm{K}$ (lower limit), depending on the clumps. The ammonia distributions are generally consistent with estimates from our single-dish results already published. The distributions of ammonia were compared with those of continuum and several other molecular lines.
O i Line Emission in the Quasar PG 1116+215
Authors: Matsuoka Yoshiki , Oyabu Shinki , Tsuzuki Yumihiko , Kawara Kimiaki , Yoshii Yuzuru
Published: March 2014

By observing the near-infrared spectrum of the quasar PG 1116$+$215 at $z = 0.176$ and combining with the HST/FOS spectrum, we obtained the relative strengths of three permitted O i lines ($\lambda$1304, $\lambda$8446, and $\lambda$11287) in a quasar for the first time. The photon flux ratios of the O i lines of the quasar were compared with those previously measured in a Seyfert 1 and six narrow-line Seyfert 1 s. No significant differences were found in the O i line flux ratios between the quasar and the other Seyferts, suggesting that the gas density in the O i and Fe ii line-emitting regions in the quasar is of the same order as those in low-luminosity AGNs. It was also found that the line width of O i$\lambda$11287 is significantly narrower than that of Ly$\alpha$, which is consistent with O i and Fe ii emission occurring in the partly ionized regions at the outermost portion of the broad-line region where velocities are small.
New High-Redshift Galaxies at z = 5.8–6.5 in the Subaru Deep Field
Authors: Shioya Yasuhiro , Taniguchi Yoshiaki , Ajiki Masaru , Nagao Tohru , Murayama Takashi , Sasaki Shunji S. , Sumiya Ryoko , Hatakeyama Yuichiro , Kashikawa Nobunari
Published: March 2014

In order to search for high-redshift galaxies around $z \sim 6$ in the Subaru Deep Field, we have investigated NB816-dropout galaxies where NB816 is the narrow-band filter centered at 815 nm with FWHM of 12.5 nm for Suprime-Cam on the Subaru Telescope. Since the NB816 imaging is so deep, we can detect 10 well-defined NB816-dropout galaxies that are identified as objects at $z = 5.8 \hbox{--} 6.5$. We discuss their observational properties.
Multi-Epoch VERA Observations of H2O Masers in OH 43.8−0.1
Authors: Honma Mareki , Bushimata Takeshi , Choi Yoon Kyung , Fujii Takahiro , Hirota Tomoya , Horiai Koji , Imai Hiroshi , Inomata Noritomo , Ishitsuka Jose , Iwadate Kenzaburo , Jike Takaaki , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Miyaji Takeshi , Nakagawa Akiharu , Nakashima Kouichirou , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Rioja Maria , Sakai Satoshi , Sato Katsuhisa , Sasao Tetsuo , Shibata Katsunori M. , Shimizu Rie , Sora Kasumi , Suda Hiroshi , Tamura Yoshiaki , Yamashita Kazuyoshi
Published: March 2014

We report on multi-epoch observations of $\mathrm{H}_2\mathrm{O}$ maser emission in the star-forming region OH 43.8$-$0.1, carried out with VLBI Exploration of Radio Astrometry. The large-scale maser distributions obtained by single-beam VLBI mapping reveal new maser spots scattered over the area of ${0\rlap {.}{}^{\mathrm {\prime \prime }}7} \times {1\rlap {.}{}^{\mathrm {\prime \prime }}0}$, in addition to a ‘shell-like’ structure with a scale of ${0\rlap {.}{}^{\mathrm {\prime \prime }}3} \times {0\rlap {.}{}^{\mathrm {\prime \prime }}5}$, which was mapped previously. Proper motions were also obtained for 43 spots based on 5-epoch monitoring with a time span of 281 days. The distributions of the proper motions show a systematic outflow in the north-south direction with an expansion velocity of $\sim 8 \,\mathrm{km} \,\mathrm{s}^{-1}$. The overall distributions of the maser spots as well as the proper motions are better represented by a bipolar flow plus a central maser cluster with a complex structure, rather than a shell with uniform expansion, such as those found in Cep A R5 and W75N VLA2. The distance to OH 43.8$-$0.1 was also estimated based on the statistical parallax, yielding $D = 2.8 \pm 0.5 \,\mathrm{kpc}$. This distance is consistent with a near kinematic distance, and rules out a far kinematic distance ($\sim 9 \,\mathrm{kpc}$). Also, the radial velocity of the OH 43.8$-$0.1 combined with the distance provides a constraint on the flatness of the galactic rotation curve, indicating that there is no systematic difference in the rotation speeds at the Sun and at the position of OH 43.8$-$0.1, which is located at a galacto-centric radius of $\sim 6.3 \,\mathrm{kpc}$.
Search for C2− in Diffuse Clouds
Authors: Civiš Svatopluk , Hosaki Yukio , Kagi Eriko , Izumiura Hideyuki , Yanagisawa Kenshi , Šedivcová Tereza , Kawaguchi Kentarou
Published: March 2014

A search has been carried out for the $\mathrm{C}_2^{-}$ ion in diffuse clouds toward HD 23180, HD 24912, HD 24398, HD 46711, and HD 50064 using the HIDES spectrometer on the Okayama 188-cm telescope. An upper limit of $8.3 \times 10^{10}\hbox{--} 1.8\times 10^{12} \,\mathrm{cm}^{-2}$ was obtained for the $\mathrm{C}_2^{-}$ column density. The upper limit value ($3.8 \times 10^{11} \,\mathrm{cm}^{-2}$) toward HD 23180 is two orders of magnitude smaller than that of the $\mathrm{C}_2$ radical. Possible production mechanisms for $\mathrm{C}_2^{-}$ are discussed.
Infrared Emission from Intracluster Dust Grains and Constraints on Dust Properties
Authors: Yamada Kenkichi , Kitayama Tetsu
Published: March 2014

For 117 clusters of galaxies, we explore the detectability of intracluster dust grains by current and future infrared facilities, taking into account both collisional heating and sputtering of grains by the ambient plasma. If the dust grains are injected into intergalactic space with the amount and size comparable to the Galactic values, the dust-to-gas ratio is typically $10^{-6}$ and the mean dust temperature is $\sim 30 \,\mathrm{K}$ near the cluster center. The predicted infrared intensities lie marginally above the detection thresholds for Spitzer Space Telescope, ASTRO-F, Herschel, and SPICA missions. For some nearby clusters, such as Perseus, A3571, A2319, A3112, and A2204, good detections of intracluster dust signals are expected in the 70$\, {\mu \mathrm {m}}$ band. Given rather tight constraints on the dust temperature from the observed electron density and the temperature, the dust mass can be inferred directly from infrared observations. Further constraints on the size distribution will be obtained once multi-band data are available. They will definitely provide a powerful probe of the dust injection processes and dust-gas interactions in intergalactic space.
Three Spectral States of the Disk X-Ray Emission of the Black-Hole Candidate 4U 1630−47
Authors: Abe Yukiko , Fukazawa Yasushi , Kubota Aya , Kasama Daisuke , Makishima Kazuo
Published: March 2014

We studied a time history of X-ray spectral states of a black-hole candidate, 4U 1630$-$47, utilizing data from a number of monitoring observations with the Rossi X-Ray Timing Explorer over 1996–2004. These observations covered five outbursts of 4U 1630$-$47, and recorded typical features of the high/soft states. The spectra in the high/soft states can be classified into three states. The first state is explained by a concept of the standard accretion disk picture. The second appears in the very high state, where a dominant hard component is seen and the disk radius apparently becomes too small. These phenomena are explained by the effect of inverse Compton scattering of disk photons, as shown by Kubota, Makishima, and Ebisawa (2001, ApJ, 560, L147) for GRO J1655$-$40. The third shows that the disk luminosity varies in proportion to $T_{\mathrm{in}}^2$, rather than $T_{\mathrm{in}}^4$, where $T_{\mathrm{in}}$ is the inner-disk temperature. This state suggests an optically-thick and advection-dominated slim disk, as given by Kubota and Makishima (2004, ApJ, 601, 428) for XTE J1550$-$564. The second and third states appear, with good reproducibility, when $T_{\mathrm{in}}$ and the total X-ray luminosity are higher than 1.2 keV and $\sim 2.5 \times 10^{38} (D/10 \,\mathrm{kpc})^2 [\cos \theta / (1/\sqrt{3})]^{-1} \,\mathrm{erg} \,\mathrm{s}^{-1}$, respectively, where $D$ is the distance to the object and $\theta$ is the inclination angle to the disk. The results suggest that these spectral states commonly appear among black-hole binaries under high accretion rates.
Quasi-Periodic Oscillations Resonantly Induced on Spin-Induced Deformed-Disks of Neutron Stars
Authors: Kato Shoji
Published: March 2014

We consider the situation where a spin-induced wavy perturbation is present on disks of neutron-star low-mass X-ray binaries. By non-linearly coupling with the perturbation, some modes of disk oscillations resonantly interact with the disks. We examine the resonant conditions under the assumption that the disks are vertically isothermal. The results show that when the spin frequency has some particular values, resonant coupling occurs at some radii. The modes and frequencies of these resonant oscillations are summarized. Some of these resonant oscillations seem to explain the frequencies of the observed kHz QPOs in objects of which the spin frequency is known.
Fourier Phase Analysis of SDSS Galaxies
Authors: Hikage Chiaki , Matsubara Takahiko , Suto Yasushi , Park Changbom , Szalay Alexander S. , Brinkmann Jon
Published: March 2014

We present a first analysis of the clustering of SDSS galaxies using the distribution function of the sum of Fourier phases over three closed wavevectors. Since the Fourier phases are statistically independent of the Fourier amplitudes, the phase statistics plays a complementary role to the conventional two-point statistics of galaxy clustering. We find that the observed distribution functions of the phase sum are in good agreement with the lowest-order approximation from perturbation theory. From comparison of observations with mock catalogs constructed from $N$-body simulations, we find that the observed phase correlations for the galaxies within the range of the absolute magnitude, $-22 < M_r <-18$, agree well with those for $\Lambda$-dominated spatially flat cold dark matter predictions with $\sigma_8 = 0.9$ evolved from the Gaussian initial condition. This agreement implies that the galaxy biasing is approximately linear in redshift space. Instead, assuming that the galaxy biasing is described by a quadratic deterministic function $\delta_{\mathrm{g}} = b_1 \delta_{\mathrm{m}} + (b_2/2)(\delta_{\mathrm{m}}^2-\langle \delta_{\mathrm{m}}^2 \rangle)$ at scale larger than $30 \, h^{-1} \,\mathrm{Mpc}$, we find that the resulting $b_2/b_1$ is well fitted by $b_2/b_1 = 0.54(\pm 0.06)-0.62(\pm 0.08) \,\sigma_8$ and is almost insensitive to the cosmology and luminosity in those ranges. Indeed, $b_2/b_1$ is nearly zero when $\sigma_8 = 0.9$.
Asymmetric Sub-Reflectors for Spherical Antennas and Interferometric Observations with an FPGA-Based Correlator
Authors: Takeuchi Hiroshi , Kuniyoshi Masaya , Daishido Tsuneaki , Asuma Kuniyuki , Matsumura Nobuo , Takefuji Kazuhiro , Niinuma Kotaro , Ichikawa Hajime , Okubo Riki , Sawano Akihiro , Yoshimura Naoya , Fujii Fumiyuki , Mizuno Keiju , Akamine Yukinori
Published: March 2014

The Nasu Radio Interferometer, consisting of eight equally spaced, 20-m diameter fixed spherical antennas, was developed for the purpose of surveying unknown variable radio sources at 1.4 GHz. An asymmetrical Gregorian sub-reflector was designed and installed on each antenna for the purpose of correcting aberrations caused by the spherical reflector. The total collecting area is $2512 \,\mathrm{m}^2$ and the field-of-view of each antenna is $ {0\rlap {.}{}^{\mathrm {\circ }}6} \times {0\rlap {.}{}^{\mathrm {\circ }}6}$. In survey observations a spatial-fast Fourier-transform (FFT)-type multi-beam system will be used. We report on the design of spherical reflectors and a digital back-end system, the basic principle of spatial-FFT image forming, and a result of interferometric observations with an FPGA-based digital correlator.
Eclipsing Light-Curve Asymmetry for Black-Hole Accretion Flows
Authors: Watarai Ken-ya , Takahashi Rohta , Fukue Jun
Published: March 2014

We propose an eclipsing light-curve diagnosis for black-hole accretion flows. When emission from an inner accretion disk around a black hole is occulted by a companion star, the observed light curve becomes asymmetric at ingress and egress on a time scale of 0.1–1 seconds. This light-curve analysis provides a means of verifying the relativistic properties of the accretion flow, based on the special/general relativistic effects of black holes. The “skewness” for the eclipsing light curve of a thin disk is $\sim 0.08$, whereas that of a slim disk is $\sim 0$, since the innermost part is self-occulted by the disk’s outer rim.
GRAPE-6A: A Single-Card GRAPE-6 for Parallel PC-GRAPE Cluster Systems
Authors: Fukushige Toshiyuki , Makino Junichiro , Kawai Atsushi
Published: March 2014

In this paper, we describe the design and performance of GRAPE-6A, a special-purpose computer for gravitational many-body simulations. It was designed to be used with a PC cluster, in which each node has one GRAPE-6A. Such a configuration is particularly cost-effective in running parallel tree algorithms. Though the use of parallel tree algorithms was possible with the original GRAPE-6 hardware, it was not very cost-effective since a single GRAPE-6 board was still too fast and too expensive. Therefore, we designed GRAPE-6A as a single PCI card to minimize the reproduction cost and to optimize the computing speed. The peak performance is 130 Gflops for one GRAPE-6A board and 3.1 Tflops for our 24 node cluster. We describe the implementation of the tree, TreePM and individual timestep algorithms on both a single GRAPE-6A system and GRAPE-6A cluster. Using the tree algorithm on our 16-node GRAPE-6A system, we can complete a collisionless simulation with 100 million particles (8000 steps) within 10 days.
Relativistic Radiative Flow in a Luminous Disk
Authors: Fukue Jun
Published: March 2014

Radiatively driven transfer flow perpendicular to a luminous disk was examined under a fully special relativistic treatment, taking into account radiation transfer. The flow was assumed to be vertical, and the gravity, the gas pressure, and the viscous heating were ignored. In order to construct the boundary condition at the flow top, the magic speed above the flat source was re-examined, and it was found that the magic speed above a moving source can exceed that above a static source ($\sim 0.45 \,c$). Then, the radiatively driven flow in a luminous disk was numerically solved, from the flow base (disk “inside”), where the flow speed is zero, to the flow top (disk “surface”), where the optical depth is zero. For a given optical depth and appropriate initial conditions at the flow base, where the flow starts, a loaded mass in the flow was obtained as an eigenvalue of the boundary condition at the flow top. Furthermore, a loaded mass and the flow final speed at the flow top were obtained as a function of the radiation pressure at the flow base; the flow final speed increases as the loaded mass decreases. Moreover, the flow velocity and radiation fields along the flow were obtained as a function of the optical depth. Within the present treatment, the flow three velocity $v$ is restricted to be within the range of $v < c/\sqrt{3}$, which is the relativistic sound speed, due to the relativistic effect.
Observations of Stellar Maser Sources with No IRAS Counterpart
Authors: Deguchi Shuji , Nakashima Jun-ichi , Miyata Takashi , Ita Yoshifusa
Published: March 2014

We investigated stellar maser sources with no IRAS counterpart at the radio, middle-infrared, and near-infrared wavelengths. A 43 GHz SiO maser search for 120 2MASS/MSX objects, and 10 OH 1612 MHz sources with no or a very faint MSX counterpart, resulted in 43 SiO detections: one OH 1612 MHz source, 2 near-infrared stars, and 40 MSX sources. Additional near-infrared $J$-, $H$-, and $K$-band observations of the OH 1612 MHz sources detected 5 near-infrared counterparts. Furthermore, middle-infrared imaging observations at 8.8, 9.7, 12.4, and 24.5$\, {\mu \mathrm {m}}$ with the Subaru 8.2-m telescope found counterparts for 2 near-infrared stars with SiO masers, and counterparts for 6 OH 1612 MHz sources. However, 4 OH 1612 MHz sources were not detected in the sensitive near- and middle-infrared searches; three of these are relatively strong OH maser sources for which the positions were known accurately. We conclude that one of these (OH 028.286$-$01.801) must be a young object in a star-forming region.
Observations of Prominence Eruptions with Two Radioheliographs, SSRT, and NoRH
Authors: Grechnev Victor V. , Uralov Arkadiy M. , Zandanov Vasily G. , Baranov Nikolai Y. , Shibasaki Kiyoto
Published: March 2014

We address simultaneous observations of eruptive prominences with two radioheliographs, SSRT at 5.7 GHz and NoRH at 17 and 34 GHz. Three events are presented: 1997 September 27, 2000 September 4, and 2001 January 14. We analyze them using images observed in microwaves, $\mathrm{H}\alpha$, images from Extreme ultraviolet Imaging Telescope on board Solar and Heliospheric Observatory (SOHO), and white-light images from Large Angle and Spectrometric Coronagraph (SOHO/LASCO). We address three stages of the eruptive process: 1) pre-eruptive ascent, 2) rapid acceleration, 3) free expansion, and the overall kinematics of the ejecta. We estimate the densities and kinetic temperatures of prominences, and also the velocities and accelerations of ejecta. The main body of a prominence is surrounded by low-density cool extensions mixed with the coronal plasma, but the transition from the cool prominence to the hot plasma is sharp. From microwave and LASCO observations with overlapping fields of view we identify a radio prominence and a core of a coronal mass ejection (CME). Their temperature remains at about 5000 K, while the brightenings observed in extreme ultraviolet are probably due to only skin-heating. We discuss the observations in terms of our Dual-Filament CME initiation model.
The Expanding Radio Lobe of 3C 84 Revealed by VSOP Observations
Authors: Asada Keiichi , Kameno Seiji , Shen Zhi-Qiang , Horiuchi Shinji , Gabuzda Denise C. , Inoue Makoto
Published: March 2014

The expansion and inner proper motions of a young radio lobe associated with the bright radio source 3C 84 in the Seyfert galaxy NGC 1275 have been detected by VSOP observations. These proper motions are consistent with the evolution scenario of classical double radio sources. The apparent expansion velocity is $(0.50 \pm 0.09) \:c$. The age of the radio lobe is estimated to be $(45.7 \pm 8.9) \:\mathrm{yr}$ in 2001, which is in agreement with the age previously estimated by Romney et al. (1982). The total flux density at 5 GHz increased at the end of the 1950’s, marked several peaks in the middle of the 1980’s, and is presently in a decay phase. The decay of the total flux density can naturally be explained by an adiabatic cooling due to expansion of the radio lobe, and previously measured spectral indices suggest that the emission comes from the surface of the radio lobe.
Lyα Emitters at z = 5.7 in the Subaru Deep Field
Authors: Shimasaku Kazuhiro , Kashikawa Nobunari , Doi Mamoru , Ly Chun , Malkan Matthew A. , Matsuda Yuichi , Ouchi Masami , Hayashino Tomoki , Iye Masanori , Motohara Kentaro , Murayama Takashi , Nagao Tohru , Ohta Kouji , Okamura Sadanori , Sasaki Toshiyuki , Shioya Yasuhiro , Taniguchi Yoshiaki
Published: March 2014

We present the properties of Ly$\alpha$ emitters (LAEs) at $z=5.7$ in the Subaru Deep Field. A photometric sample of 89 LAE candidates was constructed from narrow-band data down to $\mathit{NB816} = 26.0$ (AB) in a continuous $725 \,\mathrm{arcmin}^2$ area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Ly$\alpha$ luminosity function derived from the photometric sample is reproduced well by a Schechter function with $L^\star = 7.9^{+3.0}_{-2.2} \times 10^{42} \,\mathrm{erg} \,\mathrm{s}^{-1}$ and $\phi^\star = 6.3^{+3.0}_{-2.0} \times 10^{-4} \,\mathrm{Mpc}^{-3}$ for $\alpha =-1.5$ (fixed) over the whole luminosity range of $L \simeq 3 \times 10^{42} \hbox{--} 3 \times 10^{43} \,\mathrm{erg} \,\mathrm{s}^{-1}$. We then measured the rest-frame Ly$\alpha$ equivalent widths for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is $W_{0}^{\mathrm{i}} = 233 \,{Å}$. We infer that 30%-40% of LAEs at $z=5.7$ exceed $W_{0}^{\mathrm{i}} = 240 \,{Å}$. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derived the far-UV luminosity function of LAEs down to $M_{\mathrm{UV}} \simeq-19.6$ using the photometric sample, and compared it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at $z \sim 6$ have $W_{0}^{\mathrm{i}} \ge 100 \,{Å}$, in sharp contrast to lower-$z$ counterparts.
On the Spectroscopic Determination of Atmospheric Parameters and O/Fe Abundances of RR Lyrae Stars
Authors: Takeda Yoichi , Honda Satoshi , Aoki Wako , Takada-Hidai Masahide , Zhao Gang , Chen Yu-Qin , Shi Jian-Rong
Published: March 2014

In order to study how the conventional spectroscopic method based on the equivalent widths of the Fe I and Fe II lines effectively applies to determining the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_{\mathrm{t}}, [\mathrm{Fe/H}]$) of RR Lyrae variables and how accurately the abundances can be established from such constructed model atmospheres, we analyzed 15 high-dispersion spectrograms of RR Lyr, DX Del, DH Peg, and VY Ser taken at several different phases by using the HDS spectrograph of the Subaru Telescope, and examined the consistency of the resulting phase-to-phase abundances. Taking oxygen as the target element along with Fe, we determined its non-LTE abundance from the O I 6155–8 and 7771–5 triplets. It was found that consistent abundances were obtained for O as well as Fe to a level of $\sim 0.1 \,\mathrm{dex}$, irrespective of the pulsation phase, except for the special near-maximum high-temperature phase. This suggests that classical model atmospheres are reliably applicable to abundance determinations of RR Lyrae stars in most cases. While the oxygen abundances derived from O I 7771–5 well correlate with those from O I 6155–8, the former tends to be systematically larger by 0.1–0.2 dex than the latter, which may be interpreted as being due to the depth-dependence of the microturbulence increasing with height; i.e., the $v_{\mathrm{t}}$ value derived from deep-forming Fe lines of weak/medium-strength may not be simply applied to higher forming strong lines, such as O I 7771–5.
Velocity-Dependent Eddington Factor in Relativistic Radiative Flow
Authors: Fukue Jun
Published: March 2014

We propose a variable Eddington factor, depending on the flow velocity, $v$, for relativistic radiative flow, whose velocity becomes on the order of the speed of light. When the gaseous flow is radiatively accelerated up to the relativistic regime, the velocity gradient becomes very large in the direction of the flow. As a result, the radiative diffusion may become anisotropic in the comoving frame of the gas. Hence, in a flow that is accelerated from subrelativistic to relativistic regimes, the Eddington factor should be different from $1/3$, even in the diffusion limit. As a simple form, the velocity-dependent Eddington factor may be written as $f(\beta) = 1/3 + (2/3)\,\beta$, where $\beta = v/c$. Using the velocity-dependent Eddington factor, we can solve the rigorous equations of the relativistic radiative flow accelerated up to the relativistic speed. We also propose a generalized form for a variable Eddington factor as a function of the optical depth, $\tau$, as well as the flow velocity, $f(\tau, \beta) = 1/3 + (2/3) [{1+(\tau+1)\beta}]/({1+\tau+\beta})$, for a spherically symmetric case. The velocity-dependent Eddington factor can be used in various relativistic radiatively-driven flows, such as black-hole accretion flows, relativistic astrophysical jets and outflows, and relativistic explosions like gamma-ray bursts.
How Do We See a Relativistic Accretion Disk during a Thermal Instability?
Authors: Kawata Akihiro , Watarai Ken-ya , Fukue Jun
Published: March 2014

We calculated bolometric images of relativistic slim disks during a radiation-pressure-driven thermal instability. When the mass-accretion rate exceeds the critical one, an inner region of the standard accretion disk bursts to change to a slim disk state having a large scale height. That is, the inner region of the disk becomes high temperature, and the thickness of the disk increases due to an increase of the radiation pressure. As a result, we found that the observed image of the disk during the burst strongly depends on the inclination angle. That is, radiation from the innermost disk would be occulted by the disk outer rim for high inclination angles ($i \gtrsim 70^\circ$). We also calculated the spectral energy distribution during a thermal instability. The Wien peak of the spectrum of high inclination angles becomes softer than that of low inclination angles due to the geometrical thickness. From these facts, even if a burst occurs in a black-hole candidate, we may not observe the burst when the inclination angle is large. We may suggest that numerous luminous black-hole candidates are still hidden in our Galaxy.