bluuebunny/crossref_metadata_2025 huggingface dataset:
Near-Infrared Observations of S 255-2 : The Heart of a Massive YSO Cluster
Authors: Itoh Yoichi , Tamura Motohide , Suto Hiroshi , Hayashi Saeko S. , Murakawa Koji , Oasa Yumiko , Nakajima Yasushi , Kaifu Norio , Kosugi George , Usuda Tomonori , Doi Yoshiyuki
Published: March 2014

High-resolution near-infrared ($J$$H$$K$$L^\prime$$M^\prime$) images of a massive star-forming region, S 255-2, were obtained with the Subaru Telescope and an infrared camera, CIAO. These images clearly resolve two sets of bipolar nebulae illuminated by two independent massive YSOs. A number of cluster member YSOs have been detected, including 3 new sources. Seven early-B type stars have been identified within 10 pc of S 255-2; three are associated with extended optical H II regions. The variation in the appearance of these early-B type stars suggests an evolutionary sequence of massive stars in the S 255 region.
SiO Maser Survey in the Galactic Center Region with a Multi-Beam Receiver
Authors: Miyazaki Atsushi , Deguchi Shuji , Tsuboi Masato , Kasuga Takashi , Takano Shuro
Published: March 2014

We have made a wide-field survey of SiO masers in the $7'' \times 13''$ area around the Galactic center with the Nobeyama 45-m radio telescope using a $2 \times 3$ multi-beam SIS mixer receiver at 43 GHz. We detected 9 SiO maser sources (6 of them are new); newly detected 6 sources have been identified with Miras or OH 1612 MHz maser sources. The source surface number density, $\sim 360$ per square degree, found in this survey is slightly smaller than the number density of OH 1612 MHz sources in the same area. A least-squares analysis of the radial velocities of the detected sources has revealed a rapid rotation of the stars around the Galactic center. This implies that most of the objects detected in this survey belong to the nuclear disk near the Galactic center.
ASCA Observation of the Millisecond Pulsar PSR J2124$-$3358
Authors: Sakurai Ikuya , Kawai Nobuyuki , Torii Ken’ichi , Negoro Hitoshi , Nagase Fumiaki , Shibata Shinpei , Becker Werner
Published: March 2014

The isolated 4.9 ms pulsar PSR J2124$-$3358 was observed with ASCA on 1998 May 9, and the X-ray spectrum in the 0.5–10 keV band was obtained. The X-ray spectrum can be fitted with a single blackbody model with a temperature $kT = 0.31^{+0.08}_{-0.06}\,\mathrm{keV}$, although a simple power-law model with a relatively large photon index $\Gamma = 2.8^{+0.6}_{-0.5}$ cannot be rejected.
The r-Process Nucleosynthesis in Neutrino-/Magnetocentrifugally-Driven Winds
Authors: Nagataki Shigehiro , Kohri Kazunori
Published: March 2014

We consider the effects of the rotation and magnetic fields on the rapid neutron capture nucleosynthesis (r-process nucleosynthesis) in neutrino-driven winds. We examine the features of steady and subsonic wind solutions which extend the model of Weber and Davis (1967, Astron. Jahresber. 67.6776), which is a representative solar-wind model. Then, we find that the entropy per baryon becomes lower and the dynamical timescale becomes longer as the angular velocity becomes higher. The results are inappropriate for the production of r-process nuclei. Therefore, we conclude that it is difficult to realize a successful r-process nucleosynthesis in this framework.
Solar Models with Helioseismic Constraints and the Solar Neutrino Problem
Authors: Watanabe Satoru , Shibahashi Hiromoto
Published: March 2014

Imposing a constraint of the sound-speed profile determined from helioseismology and updating the microphysics, we have revised our seismic solar model, constructed with the assumption of a homogeneous metal abundance distribution, and have shown that the theoretically expected neutrino fluxes are still significantly more than the observations. With the same sound-speed profile constraint, we also constructed solar models with low metal abundance in the core, and evaluated the neutrino fluxes of these models to see if nonstandard solar models with a low metal core can solve the solar neutrino problem. Some of these models are in agreement with the Homestake data, the Super-Kamiokande data, and the sound-speed profile simultaneously, but none of these satisfy both the neutrino flux data, including GALLEX and SAGE, and the helioseismically determined density profile.
Specifying the Environments around GRB, Explaining the Fe Line in the X-Ray Afterglow of GRB 000214
Authors: Kotake Kei , Nagataki Shigehiro
Published: March 2014

We present a model for explaining the Fe K$\alpha$ line and the continuum in the afterglow of GRB 000214. In this paper, we pose the importance to seek the physically natural environment around GRB 000214. For reproducing the observation, we need a ring-like remnant around the progenitor, like that of SN 1987A produced by the mass-loss of the progenitor and the fireball spread over all directions. The observation of GRB 000214, in which the continuum power-law spectrum decreased faster than the line, motivated us to consider two independent systems for the line emission and the continuum spectrum. At first, the continuum spectrum can be fitted by the afterglow emission of the fireball pointing toward the observer, which does not collide with the ring because the emission of GRB and the afterglow are highly collimated to the observer by the relativistic beaming effect. Secondly, the line can be fitted by the fluorescence of the Fe atoms in the ring illuminated by the X-ray afterglow. The significance of this study is that our model may strongly constrain the GRB model.
Revisiting the Faint Blue Galaxy Problem
Authors: Mihara Kuniko
Published: March 2014

We have investigated whether the pure luminosity evolution (PLE) model in a flat universe with cosmological constant $\Lambda$ can explain the faint blue galaxy (FBG) problem in light of recent observations of a morphologically divided number count, redshift distribution, and color distribution. While the original FBG problem means an inconsistency between the total number count and redshift distribution at around $B > 22\,\mathrm{mag}$, we consider here the FBG problem in a broader context. In particular, we pay attention to an evolution model of irregular galaxies, of which predictions from the standard model disagree with recent observations. In addition to the standard 'S model' with slow star formation, we introduce a non-standard 'R model' with rapid star formation for irregular galaxies, and investigate the properties of the sum of these models (S+R model). The observed total number count and redshift distribution in the $B$-band can be well reproduced by the PLE model in a $\Lambda$-dominated universe. As for irregular galaxies, while the S model underproduces the observed count, the S+R model can account for the observation. Considering that the observed color distribution of faint irregular galaxies is very broad, we propose a possibility that irregular galaxies are composed of at least two populations.
NIR Narrow- and Broad-Band Study of the SSA 22 Field
Authors: Tamura Naoyuki , Ohta Kouji , Maihara Toshinori , Iwamuro Fumihide , Motohara Kentaro , TAkata Tadafumi , Iye Masanori
Published: March 2014

Deep narrow- and broad-band near-infrared imaging observations of the central $ {2{}^{\mathrm {\prime }}} \times {2{}^{\mathrm {\prime }}}$ region of the SSA 22 field were made with the near-infrared camera (CISCO) attached to the Subaru Telescope. Using a narrow-band filter centered at $2.033\, {\mu \mathrm {m}}$, [O III] $\lambda~5007$ emitters at $z \sim 3.06 \pm 0.02$ were searched to examine star-forming activities in an over-density region where a clustering of Lyman Break Galaxies (LBGs) and Lyman $ \alpha$ emitter candidates around $ z = 3.09$ was reported, though the targeted redshift is slightly different from that of the peak of the over-density region. Although one emitter candidate at $ z = 3.06$ was detected, it is likely to be located at a redshift of between 1 and 2 judged based on multi-band photometry. Another emission-line object was detected in another narrow-band filter (“off band” filter) centered at $ 2.120\, {\mu \mathrm {m}}$, which is identified with a galaxy at $ z = 0.132$ (the emission line is Paschen $\alpha$). The $ K^{\prime}$-band imaging data revealed the presence of 12 Extremely Red Objects (EROs) with $I_{814}-K^{\prime} \geq4$. The distribution of the EROs does not seem to coincide with that of Lyman Break Galaxies or Lyman $\alpha $ emitters at $ z \sim3$. The magnitudes and colors of the EROs are not consistent with those of passively evolving massive elliptical galaxies at $ z \sim3$. Candidates for counterparts of the submm sources detected with SCUBA are found; no EROs around the submm sources are found in our magnitude limit.
Changing Supercycle of the ER UMa-Type Star V1159 Ori
Authors: Kato Taichi
Published: March 2014

We examined the VSNET light curve of the ER UMa-type star V1159 Ori. We detected a large variation of the supercycle (the interval between successive superoutbursts) between extremes of 44.6 and 53.3d. The outburst activity was also found to decrease when the supercycle was long. The observed variation of the supercycle corresponds to a variation of $ \sim 40\%$ of the mass-transfer rate from the secondary star, totally unexpected for this class of objects. We also detected a hint of $ \sim 1800 \,\mathrm{d}$ periodicity in the variation, whose period is close to what has been suggested for solar-type cycles for cataclysmic variables (CVs). If this periodicity is caused by the magnetic activity of the secondary star, this detection constitutes the first clear evidence of continuing magnetic activity in CV evolution, even after crossing the period gap. This activity may partly explain still poorly understood origins of the high mass-transfer rates in ER UMa-type stars.
Stability of the GJ 876 Planetary System
Authors: Kinoshita Hiroshi , Nakai Hiroshi
Published: March 2014

The newly discovered planetary system of the GJ 876 is stabilized by a 2:1 mean-motion resonance. We carried out numerical simulations of the GJ 876 planetary system for several sets of initial epochs, and investigated their stability, since this planetary system is very sensitive to an initial epoch because of a large difference between the osculating elements and the mean elements.
Hubble Constant at Intermediate Redshift Using the CO-Line Tully-Fisher Relation
Authors: Tutui Yoshinori , Sofue Yoshiaki , Honma Mareki , Ichikawa Takashi , Wakamatsu Ken-ichi
Published: March 2014

We have determined distances and Hubble ratios for galaxies at intermediate redshifts, $cz \sim 10000$ to $35000 \,\mathrm{km} \,\mathrm{s}^{-1}$, by applying the CO-line Tully–Fisher relation to our $^{12}CO (J=1 - 0)$-line observations using the Nobeyama 45-m telescope, and near-IR (NIR) photometry in the $J$ - and $H$-bands using the 1.88-m telescope at Okayama Astrophysical Observatory. By averaging the Hubble ratios from the $J$-band result, we obtained a Hubble constant of $H_0 = 60 \pm 10 \mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{Mpc}^{-1}$. We argue that the CO line–NIR Tully–Fisher relation can be a complimentary method to the other methods for measuring the distances of galaxies at intermediate and high redshifts.
A CO Outflow and a Molecular Cloud Core Associated with a Young Massive Star IRAS 22134$+$5834
Authors: Dobashi Kazuhito , Uehara Hayato
Published: March 2014

We present the results of the recent 12CO ($J=1$-0), 13CO ($J=1-0$), and C 18O ($J=1-0$) observations carried out toward a bright IRAS point source (22134$+$5834) using the 45 m telescope at Nobeyama Radio Observatory (NRO) equipped with the 4 multi-beam receiver system. The IRAS source exhibits a cold color spectrum in the far infrared wavelengths and has a high luminosity of $\simeq 1700 \,{{{L}_{\odot}}}$ at the adopted distance of 900 pc, indicating that the IRAS source is a good candidate for an embedded young massive star whose luminosity is equivalent to that of an early B-type star having $\simeq 8 \,{{{M}_{\odot}}}$. A bipolar outflow and a dense core associated with IRAS 22134$+$5834 were detected by the present observations. It is remarkable that the outflow has a very large total molecular mass of $26 \,{{{M}_{\odot}}}$, which makes this source one of the most massive outflows reported to date. We derived the dynamical time scale ($\simeq 7\times 10^4 \,\mathrm{yr}$), mechanical momentum ($\simeq 140 \,{{{M}_{\odot}}}\,\mathrm{km} \,\mathrm{s}^{-1}$), and kinetic energy ($\simeq 400 \,{{{M}_{\odot}}} \,\mathrm{km}^2 \,\mathrm{s}^{-2}$) of the outflow. The dense core traced in C18O is also massive ($206 \,{{{M}_{\odot}}}$) extending over $\simeq 1 \,\mathrm{pc}$. The core shows an elliptical shape with its major axis inclined by $-45 {{}^{\circ }}$ to the north. A velocity gradient of $0.9 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{pc}^{-1}$ along the core major axis was observed, indicating a rotation of the core. We also detected blue and red velocity-shifted components in C18O along the core minor axis separated by $\simeq 0.7 \,\mathrm{km} \,\mathrm{s}^{-1}$ from the systemic velocity at $-18.2 \,\mathrm{km} \,\mathrm{s}^{-1}$, which are most likely to trace the mixture of the dense gas being swept up by the powerful outflow and the matter in the core infalling toward the central star.
Theoretical Models of Multi-Waveband QSO Luminosity Functions
Authors: Hosokawa Takashi , Mineshige Shin , Kawaguchi Toshihiro , Yoshikawa Kohji , Umemura Masayuki
Published: March 2014

The cosmological evolution of the QSO luminosity functions (LFs) at NIR/optical/X-ray bands for $1.3 \lesssim z \lesssim 3.5$ is discussed based on realistic QSO spectra. The accretion-disk theory predicts that although the QSO luminosities only depend on the mass-accretion rate, $\dot{M}$, the QSO spectra have dependence on the black-hole mass, $M_\mathrm{BH}$, as well. The smaller is $M_\mathrm{BH}$ and/or the larger is $\dot{M}$, the harder does the QSO NIR/optical/UV spectrum become. We modeled the disk spectra which can reproduce these features, and calculated the LFs for a redshift of $z \sim 3$ with the assumption of new-born QSOs shining at the Eddington luminosity. The main results are: (i) the LFs observed at optical and X-ray bands can be simultaneously reproduced. (ii) LFs in the optical and X-ray bands are not sensitive to $M_{\mathrm{BH}}$, while LFs at the NIR bands are; about a one order of magnitude difference is expected in the volume number densities at $L_{I, J} \sim 10^{46} \,\mathrm{erg} \,\mathrm{s}^{-1}$ between the case that all QSOs would have the same spectral shape as that of $M_\mathrm{BH} = 10^{9} \,{{{M}_{\odot}}}$ and the case with $M_\mathrm{BH} = 10^{11} \,{{{M}_{\odot}}}$. (iii) The resultant LFs at NIR are dominated by $10^{7} \,{{{M}_{\odot}}}$ black holes at $L_{I, J} \lesssim 10^{44} \,\mathrm{erg} \,\mathrm{s}^{-1}$, and by $10^{11} \,{{{M}_{\odot}}}$ black holes at $L_{I, J} \gtrsim 10^{46} \,\mathrm{erg} \,\mathrm{s}^{-1}$. Future infrared observations from space (e.g. NGST) will probe the cosmological evolution of black-hole masses. For a redshift of $z \lt 3$, on the other hand, the observed optical/X-ray LFs can be fitted if the initial QSO luminosity, $L_0$, is below the Eddington luminosity, $L_\mathrm{Edd}$. Interestingly, the best-fitted values of $\ell \equiv L_0/L_\mathrm{Edd}$ are different in the B- and X-ray bands; $\ell_{B} \approx 2.5 \, \ell_\mathrm{x}$. The reason for this discrepancy is briefly discussed.
CO ($J=6-5$) Observations of the Quasar SDSS 1044$-$0125 at $z = 5.8$
Authors: Iwata Ikuru , Ohta Kouji , Nakanishi Kouichiro , Kohno Kotaro , McMahon Richard G.
Published: March 2014

We present a result of CO ($J=6-5$) observations of a quasar SDSSp J104433.04$-$012502.2 at $z = 5.8$. Ten days of observations with the Nobeyama Millimeter Array yielded an rms noise level of $\sim 2.1 \,\mathrm{mJy}\;\mathrm{beam}^{-1}$ in a frequency range from 101.28 GHz to 101.99 GHz at a velocity resolution of $120 \,\mathrm{km} \,\mathrm{s}^{-1}$. No significant clear emission line was detected in the observed field and frequency range. The three-sigma upper limit on the CO ($J=6-5$) luminosity of the object is $2.8 \times 10^{10} \,\mathrm{K} \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{pc}^2$, corresponding to a molecular gas mass of $1.2 \times 10^{11} {{{M}_{\odot}}}$, if a conversion factor of $4.5 \,{{{M}_{\odot}}} (\mathrm{K} \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{pc}^2)^{-1}$ is adopted. The obtained upper limit on the CO luminosity is slightly smaller than those observed in quasars at $z=4-5$ toward which CO emissions are detected.
ASCA Observations on Two Molecular Cloud Cores in the Perseus Complex
Authors: Yamauchi Shigeo , Tsuboi Yohko , Koyama Katsuji
Published: March 2014

We present ASCA results for two molecular cloud cores in the Perseus complex, Barnard 1 and a cloud core which contains a class 0 protostar, IRAS 03282$+$3035. Four X-ray sources are found, of which two have either a radio, infrared, or optical counterpart. The X-ray temperature and flux of an IRAS source, IRAS 03275$+$3020/AX J0330$+$3030, are similar to those of T Tauri stars. Thus, together with the infrared and optical data, this source can be classified as a T Tauri star. Two unidentified sources have a spectrum with moderate temperature and absorption, and are possibly new young stellar objects in the clouds. A radio source, BWE 0328$+$3054/AX J0331$+$3104, has a hard X-ray spectrum fitted with a power-law model of photon index $\sim 1.5$, and hence would be an active galactic nucleus. No X-ray emission is found from a class 0 protostar, IRAS 03282$+$3035, and a class 0 candidate, IRAS 03301$+$3057.
1998 Superoutburst of the Large-Amplitude SU UMa-Type Dwarf Nova WX Ceti
Authors: Kato Taichi , Matsumoto Katsura , Nogami Daisaku , Morikawa Koichi , Kiyota Seiichiro
Published: March 2014

We observed the 1998 November superoutburst of WX Cet, a dwarf nova originally proposed as a WZ Sge-like system. The observation established that WX Cet is an SU UMa-type dwarf nova with a mean superhump period of 0.05949(1)d, which is 2.1% longer than the reported orbital period. The lack of early superhumps at the earliest stage of the superoutburst, the rapid development of usual superhumps, and the possible rapid decay of late superhumps seem to support that WX Cet is a fairly normal large-amplitude SU UMa-type dwarf nova, rather than a WZ Sge-type dwarf nova with a number of peculiarities. However, a period increase of superhumps at a rate $\dot{P}/P = +8.5\pm 1.0 \times 10^{-5}$ was observed, which is one of the largest $\dot{P}/P$ ever observed in SU UMa-type dwarf novae. A linear decline of light, with a rate of $0.10 \,\mathrm{mag} \,\mathrm{d}^{-1}$, was observed in the post-superoutburst stage. This may be an exemplification of the decay of the viscosity in the accretion disk after the termination of a superoutburst, mechanism of which is proposed to explain a variety of post-superoutburst phenomena in some SU UMa-type dwarf novae.
Sunspot Magnetic Fields Observed with a Large-Format Infrared Array
Authors: Sakurai Takashi , Yanagisawa Kenshi , Kobiki Toshihiko , Kasahara Shouichi , Nakakubo Kayoko
Published: March 2014

Spectro-polarimetric observations of sunspots were carried out by using a PtSi near-infrared camera (KONIC) of Kiso Observatory, The University of Tokyo, in the period of 1999 November 3–5. The camera was attached to a spectrograph of the Domeless Solar Telescope at Hida Observatory, Kyoto University. We observed the absorption lines of Fe I at 15648.5${Å}$ (Landè factor $g_{\mathrm{L}} = 3$) and 15652.9${Å}$ ($g_{\mathrm{L~eff}} = 1.53$), and derived the distribution of the magnetic field strengths and inclination angles across the sunspots. The ratio of the Zeeman splitting of the two lines was derived to be $0.39 \pm 0.01$, while the ratio of the Landè factors is 0.51. Our data indicates that the effective Landè factor of the 15652.9${Å}$ line is $1.17 \pm 0.03$.
Study of Molecular Clouds and Star Formation in the Region of IC 2118
Authors: Kun Maria , Aoyama Hiroko , Yoshikawa Nao , Kawamura Akiko , Yonekura Yoshinori , Onishi Toshikazu , Fukui Yasuo
Published: March 2014

We carried out a 12CO survey of molecular clouds in the region of the reflection nebula IC 2118. Our observations covered the whole area of IC 2118 ($\sim 6 \,\mathrm{deg^2}$) with a 2.$^{\prime}$6 beam at a $4^{\prime}$ grid spacing. We identified six molecular clouds. Based on a literature search we found a distance value of 210 pc for the reflection nebula and its associated molecular clouds, indicating that the clouds are probably interacting with the Orion–Eridanus Bubble. Using this distance value, we determined the physical properties of the clouds. We also made an objective prism search for $\mathrm{H}\alpha$ emission stars in the region in order to find possible solar-type stars born in the clouds, and identified 46 candidate pre-main-sequence stars. Their spectroscopic follow-up is in progress. Seven of them have so far proved to be T Tauri stars.
Large-Amplitude 2.65-d Oscillation in the VY Scl-Type Star V425 Cassiopeiae
Authors: Kato Taichi , Uemura Makoto , Ishioka Ryoko , Kinnunen Timo
Published: March 2014

From long-term photometry of a VY Scl-type star, V425 Cas, between 1998 and 2000, we discovered a short-term, large-amplitude (up to 1.5 mag) variation. The variation was well represented by a single period of 2.65 d. The large amplitude and the profile of the folded light curve suggest that the dwarf nova-type disk instability is responsible for this variation. The shortness of the period is unprecedented in hydrogen-rich cataclysmic variables. Given the recent emerging evidence that the irradiation from white dwarfs in VY Scl-type systems affect their light behavior, we propose a possibility that this unique variation in V425 Cas can be explained by the combination of the dwarf nova-type disk instability and irradiation. Similar short-period “outbursts" have been known in X-ray transients (V518 Per), and helium cataclysmic variables (CR Boo and V803 Cen). We discuss the possibility that these phenomena have a common origin to the unique variation in V425 Cas.
Photospheric Abundances of Volatile and Refractory Elements in Planet-Harboring Stars
Authors: Takeda Yoichi , Sato Bun’ei , Kambe Eiji , Aoki Wako , Honda Satoshi , Kawanomoto Satoshi , Masuda Seiji , Izumiura Hideyuki , Watanabe Etsuji , Koyano Hisashi , Maehara Hideo , Norimoto Yuji , Okada Takafumi , Shimizu Yasuhiro , Uraguchi Fumihiro , Yanagisawa Kenshi , Yoshida Michitoshi , Miyama Shoken M. , Ando Hiroyasu
Published: March 2014

By using the high-dispersion spectra of 14 bright planet-harboring stars (along with 4 reference stars) observed with the new coudé echelle spectrograph at Okayama Astrophysical Observatory, we investigated the abundances of volatile elements (C, N, O, S, Zn; low condensation temperature $T_\mathrm{c}$) in order to examine whether these show any significant difference compared to the abundances of other refractory elements (Si, Ti, V, Fe, Co, Ni; high $T_\mathrm{c}$), which are known to be generally overabundant in those stars with planets, since a $T_\mathrm{c}$-dependence is expected if the cause of such a metal-richness is due to the accretion of solid planetesimals onto the host star. We found, however, that all elements which we studied behave themselves quite similarly to Fe (i.e., $[\mathrm{X} / \mathrm{Fe}] \simeq 0$), even for the case of volatile elements. This may suggest that the enhanced metallicity in those planet-bearing stars is not so much an acquired character (by accretion of rocky material) as rather primordial.
Iodine-Cell Spectroscopy at Okayama Astrophysical Observatory: First Results
Authors: Takeda Yoichi , Sato Bun’ei , Kambe Eiji , Watanabe Etsuji , Miyazaki Hideaki , Wada Setsuko , Ando Hiroyasu , Masuda Seiji , Izumiura Hideyuki , Koyano Hisashi , Maehara Hideo , Norimoto Yuji , Okada Takafumi , Shimizu Yasuhiro , Uraguchi Fumihiro , Yanagisawa Kenshi , Yoshida Michitoshi , Okada Norio , Kawanomoto Satoshi , Miyama Shoken M.
Published: March 2014

Toward the aims of spectroscopically searching for planetary systems around stars, or detecting oscillations of solar-type stars for stellar seismology, we have started an experimental project of very precise determinations of stellar radial velocity variations based on the iodine-cell ($\mathrm{I}_{2}$ cell) technique at Okayama Astrophysical Observatory. We here report on the first preliminary results of test observations for two planet-harboring stars ($\upsilon $ And and $\tau $ Boo) based on data obtained by using the newly developed $\mathrm{I}_{2}$ cell and processed with a practical and quick analysis method. We confirmed that the internal statistical error can be as small as $5 \hbox{--} 6 \,\mathrm{m} \,\mathrm{s}^{-1}$ at best. Then, the resulting radial velocity solutions turned out to be in reasonable agreement with the well-established predicted variations over a time span of 4–5 days; the $O-C$ deviations indicate that a short-time-scale precision of $\sim 15\,\mathrm{m} \,\mathrm{s}^{-1}$ has been accomplished in a practical sense.
Collisional Evolution of Galaxy Clusters and the Growth of Common Halos
Authors: Takahashi Koji , Sensui Tomohiro , Funato Yoko , Makino Junichiro
Published: March 2014

We investigated the dynamical evolution of clusters of galaxies in virial equilibrium using Fokker–Planck models and self-consistent $N$-body models. In particular, we focused on the growth of a common halo, which is a cluster-wide halo formed by matter stripped from galaxies, and the development of a central density cusp. The Fokker–Planck models include the effects of two-body gravitational encounters both between galaxies and between galaxies and common halo particles. The effects of tidal mass stripping from the galaxies due to close galaxy–galaxy encounters and accompanying dissipation of the orbital kinetic energies of the galaxies were also taken into account in the Fokker–Planck models. We find that the results of the Fokker–Planck models are in excellent agreement with those of the $N$-body models regarding the growth of the common halo mass and the evolution of the cluster density profiles. In the central region of the cluster, a shallow density cusp, approximated by $\rho (r) \propto r^{-\alpha}$ ($\alpha \sim 1$), develops. This shallow cusp results from the combined effects of two-body relaxation and tidal stripping. The cusp steepness, $\alpha$, weakly depends on the relative importance of the tidal stripping. When the effect of stripping is important, the central velocity dispersion decreases as the central density increases and, consequently, a shallow ($\alpha <2$) cusp is formed. In the limit of no stripping, usual gravothermal core collapse occurs, i.e. the central velocity dispersion increases as the central density increases with a steep ($\alpha \gt 2$) cusp left. We conclude from our consideration of the origin of the cusp demonstrated here that shallow cusps should develop in real galaxy clusters.
IR Com: Deeply Eclipsing Dwarf Nova Below the Period Gap —A Twin of HT Cas?
Authors: Kato Taichi , Baba Hajime , Nogami Daisaku
Published: March 2014

We observed an X-ray selected, deeply eclipsing cataclysmic variable IR Com ($=\mathrm{S}~10932$). We detected an outburst occurring on 1996 January 1. The light curve of the outburst closely resembled that of a normal outburst of an SU UMa-type dwarf nova, rather than that of an intermediate polar. Time-resolved photometry during the outburst showed that eclipses became systematically deeper and narrower as the outburst faded. Full-orbit light curves in quiescence showed little evidence of orbital humps or asymmetry of the eclipses. In addition to the presence of high–low transitions in quiescence, the overall behavior of the outbursts and the characteristics of the eclipse profiles suggest that IR Com can be best understood as a twin of HT Cas, a famous eclipsing SU UMa-type dwarf nova with a number of peculiarities.
Photometry of the 1991 Superoutburst of EF Pegasi: Super-Quasi-Periodic Oscillations with Rapidly Decaying Periods
Authors: Kato Taichi
Published: March 2014

We observed the 1991 October outburst of EF Peg. Prominent superhumps with a period of 0.08705(1)d were observed, qualifying EF Peg as being a long-period SU UMa-type dwarf nova. The superhump period showed a monotonic decrease during the superoutburst, which makes a contrast to the virtually zero period change observed during the 1997 superoutburst of the same object. Large-amplitude and highly coherent quasi-periodic oscillations (super–QPOs) were observed on October 18, when superhumps were still growing in amplitude. Most strikingly, the QPOs showed a rapid decrease in the period from 18 min to 6.8 min within the 3.2-hr observing run. Such a rapid change in the period has not been observed in any class of QPOs in cataclysmic variables. We propose a hypothesis that the rapid decrease of the QPO period reflects a rapid removal of the angular momentum from an orbiting blob in the accretion disk, via viscosity in a turbulent disk. A brief comparison is given with the QPOs in X-ray binaries, some of which are known to show a similar rapid decrease in the periods.
The Contribution of Warm Gas in Cluster Galaxies to the Soft X-Ray Emission of Clusters
Authors: Cheng Ling-Mei
Published: March 2014

We investigate the possible existence and X-ray emission of warm gas associated with the gravitational potential wells of individual galaxies in rich clusters in an attempt to account for the EUV and soft X-ray excess detected in some nearby clusters. The intrinsic properties of hot intracluster gas and warm galactic gas are specified by the assumption of isothermality and the equation of hydrostatic equilibrium, and the underlying gravitational potentials are described by the universal density profile. Moreover, the Schechter luminosity function and the King model are adopted for the number and spatial distributions of the cluster galaxies, respectively. We fix the gas fraction in different galaxies using Einstein Observatory and ROSAT observations. Our numerical calculation in conjunction with Monte Carlo technique shows that cluster galaxies consisting primarily of ellipticals can make a nonnegligible contribution to the EUV and soft X-ray emission seen in the central regions of clusters. For a rich cluster, like Coma, a small fraction (6%) of soft X-ray emission in the 0.1–1 keV band may come from galaxies, while a significant excess of up to 26% in the 0.01–0.1 keV band can be attributed to galaxies. The cosmological implications and observational consequence of this alternative scenario for the EUV and soft X-ray excess in clusters are addressed.
Effect of the Polarization of Photon Splitting on the Cyclotron Lines in Large-Scale Atmospheres with Super-Strong Magnetic Fields
Authors: Nishimura Osamu
Published: March 2014

The cyclotron lines are affected by photon splitting in super-strong magnetized atmospheres ($ \sim 4.4 \times 10^{13} \,\mathrm{G}$) into which a power-law-type flux is injected. We studied the polarization effect of photon splitting on the cyclotron line formation by treating different modes of splitting. We calculated the emergent spectra for two conditions: only one splitting mode and three splitting modes that could operate in a neutron-star atmosphere with a subcritical magnetic field. Photon splitting can also operate over a larger scale than cyclotron resonant scattering in a neutron-star atmosphere, since photon splitting occurs in a super-strong magnetic field even in the absence of a plasma. We therefore considered atmospheres consisting of lower and higher density regions. Cyclotron resonant scattering is dominant in a higher density region, and photon splitting is dominant in a lower density region. In three splitting modes, we found that the cyclotron absorption lines are strongly reprocessed by photon splitting, and thus may not be detected even for a magnetic field of about $ 1.0 \times 10^{13} \,\mathrm{G}$ in the power-law-type spectra. However, we confirmed that the cyclotron absorption lines are not mostly reprocessed by photon splitting in only one splitting mode.
CISCO: Cooled Infrared Spectrograph and Camera for OHS on the Subaru Telescope
Authors: Motohara Kentaro , Iwamuro Fumihide , Maihara Toshinori , Oya Shin , Tsukamoto Hiroyuki , Imanishi Masatoshi , Terada Hiroshi , Goto Miwa , Iwai Jun’ichi , Tanabe Hirohisa , Hata Ryuji , Taguchi Tomoyuki , Harashima Takashi
Published: March 2014

This paper describes a Cooled Infrared Spectrograph and Camera for OHS (CISCO), mounted on the Nasmyth focus of the Subaru telescope. It is primarily designed as a back-end camera of the OH-Airglow Suppressor (OHS), and is also used as an independent, general-purpose near-infrared camera/spectrograph. CISCO is based on a single $ 1024 \times 1024$ format HgCdTe HAWAII array detector, and is capable of either wide-field imaging of $ {1\rlap {.}{}^{\mathrm {\prime }}8} \times {1\rlap {.}{}^{\mathrm {\prime }}8}$ field-of-view or low-resolution spectroscopy from 0.9 to 2.4 $ {\mu \mathrm {m}}$. The limiting magnitudes measured during test observations were found to be $ J=23.5 \,\mathrm{mag}$ and $ K^{\prime} = 22.4 \,\mathrm{mag}$ (imaging, $ {1{}^{\mathrm {\prime \prime }}}$ aperture, $ \mathrm{S} / \mathrm{N} = 5 $, 1 hr exposure).
Origin of the “Disk-Line” Feature in the X-Ray Energy Spectrum of a Seyfert Galaxy, NGC 4151
Authors: Takahashi Kazuki , Inoue Hajime , Dotani Tadayasu
Published: March 2014

We have studied the origin of the broad and skewed feature at 4.5–7.5 keV in the energy spectra of NGC 4151 using the ASCA and RXTE data. The feature consists of a narrow peak at 6.4 keV and a broad wing extended between 4.5–7.5 keV. An analysis of the long-term variations revealed that the feature became variable only on a time scale longer than $1.5 \times 10^6 \,\mathrm{s}$. Through a comparison with the continuum variabilities, we found that the emission region of the excess flux at 4.5–7.5 keV has an extent of $10^{17} \,\mathrm{cm}$. The broad and skewed feature at 4.5–7.5 keV may be explained by the so-called “disk-line” model. If so, the size of the line-emitting region, $10^{17} \,\mathrm{cm}$, should be equal to several or ten times the Schwarzschild radius of the central black hole. This results in a black hole mass of $10^{11} \,{{{M}_{\odot}}}$, which may be too large for NGC 4151. We propose an alternative explanation for the broad and skewed feature, i.e. a “reflection” model, which can also reproduce the overall energy spectra very well. In this model, cold matter with a sufficiently large column density is irradiated by X-rays to produce a reflected continuum, which constitutes the broad wing of the feature and narrow fluorescent lines. The equivalent width of the iron fluorescent line ($\sim 2 \,\mathrm{keV}$) and the upper limit of its width ($\sigma < 92 \,\mathrm{eV}$) are also consistent with this model. From these results and considerations, we conclude that the “disk-line” model has difficulty to explain the spectral variations of NGC 4151, and the reflection model is more plausible.
Search for Hot Gas in the Local Group with ASCA
Authors: Osone Satoko , Makishima Kazuo , Matsuzaki Keiichi , Ishisaki Yoshitaka , Fukazawa Yasushi
Published: March 2014

An X-ray study was made to examine whether some part of the soft X-ray background is coming from hot gas in the Local Group. For this purpose, four consecutive pointings were made with ASCA toward a sky region between M31 and M33, which is close to the direction of the center of the Local Group. By comparing the X-ray surface brightness in this sky direction with that in another blank sky region near the north equatorial pole, an upper limit on any soft excess X-ray background was determined to be $2.8 \times 10^{-9} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1} \,\mathrm{sr}^{-1}$ with a 90% confidence level statistical error. Assuming an optically-thin thermal bremsstrahlung energy spectrum (Raymond–Smith model) for a temperature of 1 keV and a $\beta$-model electron density distribution for a core radius of 100 kpc for the X-ray halo, the upper limit of the central plasma density was obtained to be $1.3 \times 10^{-4} \,\mathrm{cm}^{-3}$. The plasma column density is too low to contribute significantly to the observed quadrupole anisotropy in the cosmic microwave background.
Tridimensional Spectroscopic Observation of the Interacting System NGC 7592
Authors: Hattori Takashi , Yoshida Michitoshi , Ohtani Hiroshi , Ishigaki Tsuyoshi , Sugai Hajime , Hayashi Tadashi , Ozaki Shinobu , Ishii Motomi
Published: March 2014

We performed a tridimensional spectroscopic study of NGC 7592, an infrared-luminous interacting system of three galaxies, one of which contains a Seyfert 2 nucleus. Narrow-band images of $\mathrm{H}\alpha$ and [O iii] were obtained using an imaging Fabry–Perot interferometer with a tunable filter. An area-spectroscopic observation was also made by a slit scan in a direction perpendicular to the slit. The Seyfert nucleus was found to be surrounded by a knotty star-forming region of disk- or ring-shape. Along the axis of the disk or ring, a highly-ionized bipolar gaseous region was identified. From kinematical analyses, it has been suggested that this system is composed of two galaxies; one apparent nucleus is considered to be a giant H ii region belonging to one galaxy. This result is supported by the morphological properties in near-infrared. Further, it has been suggested that one galaxy is an early-type spiral, whereas the other is a late-type one, and the two galaxies show a marked difference in the distribution of the star-forming regions within each. The cause of the difference was argued in relation with the dynamical perturbation between the two galaxies.
Abundances in Comet 19P/Borrelly at the Time of the Spacecraft Encounters
Authors: Hamane Toshihiko , Kawakita Hideyo , Kinugasa Kenzo , Yamamuro Tomoyasu , Takeyama Norihide
Published: March 2014

A spectroscopic observation of comet 19P/Borrelly was carried out on 2001 September 23, using a low-dispersion spectrograph in the wavelength range 3800–7600${Å}$. It was performed about 20 hours after an encounter of the spacecraft Deep Space 1 (DS1) with the comet. We detected species such as CN, $\mathrm{C}_2$, [O i], and $\mathrm{NH}_2$, and estimated the gas-production rates of CN, $\mathrm{C}_2$, and $\mathrm{NH}_2$ relative to that of $\mathrm{H}_2\mathrm{O}$ based on a Haser model. The production-rate ratios and the gas-to-dust ratio were: $Q(\mathrm{CN}) / Q(\mathrm{H}_2\mathrm{O}) = 0.094\%$, $Q(\mathrm{C}_2)/Q(\mathrm{H}_2\mathrm{O}) = 0.096\%$, $Q(\mathrm{NH}_2)/Q(\mathrm{H}_2\mathrm{O}) = 0.13\%$, and $\log [Q(\mathrm{H}_2\mathrm{O}) / Af\rho] = 26.0$. Our calculated relative production rates of $\mathrm{C}_2$ and $\mathrm{NH}_2$ to CN were similar to those of previous apparitions. Therefore, the circumstances of the comet when DS1 encountered may be the same as those during the last several apparitions, and many ground-based observations performed during previous apparitions will be useful to reveal the nature of the comet during the in situ observations by DS1.
Modeling a Pairwise Peculiar Velocity Distribution Function of Dark Matter from Halo Density Profiles
Authors: Kuwabara Takeshi , Taruya Atsushi , Suto Yasushi
Published: March 2014

We derive the pairwise peculiar velocity distribution function of dark matter particles by applying a dark-matter halo approach. Unlike previous work, we do not assume a Gaussian velocity distribution function of dark matter in a single halo, but compute it self-consistently with the assumed density profile for the dark-matter halo. The resulting distribution function is well approximated by an exponential distribution which is consistent with the previous observational, numerical, and theoretical results. We also compute the pairwise peculiar velocity dispersion for different density profiles, and provide a practical fitting formula. We apply an empirical biasing scheme into our model and present a prediction for a pairwise peculiar velocity dispersion of galaxies, and reproduce the previous results of simulations using our semi-analytical method.
Composite Luminosity Functions Based on the Sloan Digital Sky Survey “Cut and Enhance” Galaxy Cluster Catalog
Authors: Goto Tomotsugu , Okamura Sadanori , Mckay Timothy A. , Bahcall Neta A. , Annis James , Bernardi Mariangela , Brinkmann Jonathan , Gómez Percy L. , Hansen Sarah , Kim Rita S. J. , Sekiguchi Maki , Sheth Ravi K.
Published: March 2014

We present here results on the composite luminosity functions (LF) of galaxies in the clusters of galaxies selected from the Cut and Enhance cluster catalog (CE) of the Sloan Digital Sky Survey. We constructed composite LFs in the five SDSS bands, $u, g, r, i$, and $z$, using 204 CE clusters ranging from $z = 0.02$ to $z = 0.25$ . Background and foreground galaxies were subtracted from the LF using an annular region around clusters to take large-scale, galaxy-number-count variances into consideration. A LF of each cluster was weighted according to the richness and number of contributing galaxies to construct the composite LF. Taking advantage of accurate photometry of SDSS, we used photometric redshifts to construct composite luminosity functions and thus study a large number of clusters. The robustness of the weighting scheme was tested using a Monte-Carlo simulation. The best-fit Schechter parameters are $(M^*, \alpha) = (-21.61 \pm 0.26,-1.40 \pm0.11), (-22.01 \pm 0.11,-1.00 \pm 0.06), (-22.21 \pm 0.05,-0.85 \pm 0.03), (-22.31 \pm 0.08,-0.70 \pm 0.05)$, and $(-21.36 \pm 0.06,-0.58 \pm 0.04)$ in $u, g, r, i$, and $z$, respectively. We find that the slope of composite LFs becomes flatter toward a redder color band. Compared with the field LFs of the SDSS, the cluster LFs have brighter characteristic magnitude and flatter slopes in the $g, r, i$, and $z$ bands. These results are consistent with the hypothesis that the cluster LF has two distinct underlying populations; i.e. the bright end of the LF is dominated by bright early types that follow a Gaussian-like luminosity distribution, while the faint-end of the cluster LF is a steep power-law like function dominated by star-forming (bluer) galaxies. We also studied the composite LFs for early-type and late-type galaxies using profile fits, a concentration parameter and $u-r$ color to classify galaxy morphology. A strong dependence of LF on galaxy morphology was found. The faint end slope of the LF is always flatter for early-type galaxies than late-type, regardless of the passband and methodology. These results are consistent with the hypothesis that the cluster regions are dominated by bright elliptical galaxies. This work also provides a good low-redshift benchmark for on-going multi-color photometric studies of high redshift clusters of galaxies using 4–8m class telescopes.
Extended Thermal X-Ray Emission from the Spiral-Dominant Group of Galaxies HCG 57
Authors: Fukazawa Yasushi , Kawano Naomi , Ohto Akimitsu , Mizushima Hirofumi
Published: March 2014

We observed a group of galaxies, HCG 57, with ASCA. Regardless that their member galaxies are dominated by spiral galaxies, we detected extended thermal X-ray emission that is attributed to hot gas with a temperature of $1.04\pm0.10 \,\mathrm{keV}$. This is the second clear detection of thermal X-ray emission from a spiral-dominant group of galaxies after HCG 92. The luminosity of the thermal emission is about $5\times10^{41} \,\mathrm{erg} \,\mathrm{s}^{-1}$ in the 0.5–10 keV band, which is higher than that of HCG 92, but relatively less luminous among groups of galaxies. The X-ray emission is extended over several member galaxies, and is thus associated with the group rather than an individual galaxy. The metal abundance cannot be well constrained with a lower limit of 0.08 solar. The gas-to-stellar mass ratio is $\sim0.3$. Although this is relatively low among groups, the hot gas is also a significant component even in the spiral-dominant group. We suggest that the X-ray faintness of spiral-dominant groups is due to the low surface brightness and somewhat low gas mass, at least in the case of HCG 57.
Extended Deep Minimum and Subsequent Brightening of RX And in 1996-1997
Authors: Kato Taichi , Nogami Daisaku , Masuda Seiji
Published: March 2014

We discovered that RX And, one of the prototypical Z Cam-type dwarf novae, underwent a deep, extended faint state in 1996–1997. Time-resolved photometry at the bottom of the fading revealed the presence of strong flickering, and the absence of detectable orbital modulation. This finding indicates that mass-transfer remained even at the deepest minimum of the fading, contrary to what was observed in a deep minimum of a VY Scl-type star, MV Lyr. RX And subsequently underwent a brightening (outburst) during its recovery stage. The photometric and spectroscopic characteristics of the brightening significantly differed from those of ordinary outbursts of RX And, and are considered to resemble an inside-out type outburst of a long-period dwarf nova. An examination of historical visual observations revealed the possible presence of $\sim 10{-}\mathrm{yr}$ periodicity, which is close to what has been proposed for MV Lyr. The common observed features between RX And and VY Scl-type stars may suggest a common underlying mechanism for producing temporary deep fadings. A departure from the disk instability model, as observed in VY Scl-type stars, was not apparent in the present fading of RX And. In conjunction with a recently published Hubble Space Telescope observation during the same fading, we can conclude that the phenomenological difference from the VY Scl-type fading can be understood to be a smaller effect of irradiation on the accretion disk in RX And.
Advection-Dominated Accretion Flow in the Kerr Metric: Propagation of a Wave Pattern
Authors: Musil Tomáš , Karas Vladimír
Published: March 2014

The time evolution of an advection-dominated accretion flow is explored in terms of relativistic fluid equations. An axially symmetric, vertically averaged mean flow is constructed and perturbed. An axisymmetric pattern is followed as it propagates in the form of a wave towards the horizon of a rotating black hole. Several assumptions are relaxed in comparison with previous works (Manmoto et al. 1996, AAA 65.067.206). The wave reflection and steepening are examined and the influence of black hole angular momentum is discussed.
Three-Dimensional Genus Statistics of Galaxies in the SDSS Early Data Release
Authors: Hikage Chiaki , Suto Yasushi , Kayo Issha , Taruya Atsushi , Matsubara Takahiko , Vogeley Michael S. , Hoyle Fiona , Gott J. Richard , Brinkmann Jon ,   for the SDSS collaboration
Published: March 2014

We present the first analysis of three-dimensional genus statistics for the SDSS EDR galaxy sample. Due to the complicated survey volume and the selection function, analytic predictions of the genus statistics for this sample are not feasible; therefore, we construct extensive mock catalogs from $ N$-body simulations in order to compare the observed data with model predictions. This comparison allows us to evaluate the effects of a variety of observational systematics on the estimated genus for the SDSS sample, including the shape of the survey volume, the redshift distortion effect, and the radial selection function due to the magnitude limit. The observed genus for the SDSS EDR galaxy sample is consistent with that predicted by simulations of a $ \Lambda$-dominated spatially-flat cold dark matter model. Standard ($ \Omega_0=1$) cold dark matter model predictions do not match the observations. We discuss how future SDSS galaxy samples will yield improved estimates of the genus.