bluuebunny/crossref_metadata_2025 huggingface dataset:
The Subaru Deep Field: The Optical Imaging Data
Authors: Kashikawa Nobunari , Shimasaku Kazuhiro , Yasuda Naoki , Ajiki Masaru , Akiyama Masayuki , Ando Hiroyasu , Aoki Kentaro , Doi Mamoru , Fujita Shinobu S. , Furusawa Hisanori , Hayashino Tomoki , Iwamuro Fumihide , Iye Masanori , Karoji Hiroshi , Kobayashi Naoto , Kodaira Keiichi , Kodama Tadayuki , Komiyama Yutaka , Matsuda Yuichi , Miyazaki Satoshi , Mizumoto Yoshihiko , Morokuma Tomoki , Motohara Kentaro , Murayama Takashi , Nagao Tohru , Nariai Kyoji , Ohta Kouji , Okamura Sadanori , Ouchi Masami , Sasaki Toshiyuki , Sato Yasunori , Sekiguchi Kazuhiro , Shioya Yasunori , Tamura Hajime , Taniguchi Yoshiaki , Umemura Masayuki , Yamada Toru , Yoshida Makiko
Published: March 2014

The Subaru Deep Field (SDF) project is a program of Subaru Observatory to carry out a deep galaxy survey over a blank field as large as $34' \times 27'$. The program consists of very deep multi-band optical imaging, near-infrared imaging for smaller portions of the field, and follow-up optical spectroscopy. The major scientific goals of the project are to construct large samples of Lyman-break galaxies at $z \simeq 4 \hbox{--} 5$ and Lyman alpha emitters at $z \simeq 5.7$ and 6.6, and to make detailed studies of these very high-redshift galaxy populations. In this paper, we describe the optical imaging observations and data reduction, presenting mosaicked images and object catalogs in seven bandpasses. The optical imaging was made through five broad-band filters, $B$, $V$, $R$, $i'$, $z'$, and two narrow-band filters, NB816 ($\lambda_{\mathrm{c}} = 8150 \,{Å}$) and NB921 ($\lambda_{\mathrm{c}}=9196 \,{Å}$) with almost 10 hour integrations for each band. The limiting magnitudes measured at $3 \,\sigma$ on a $2^{\prime\prime}$ aperture are $B=28.45$, $V=27.74$, $R=27.80$, $i'=27.43$, $z'=26.62$, $\mathrm{NB816} = 26.63$, and $\mathrm{NB921}=26.54$ in the AB system. The object catalog constructed for each of the seven bands contains more than $10^5$ objects. The galaxy number counts corrected for detection incompleteness and star-count contributions are found to be consistent with previous results in the literature. Mosaicked images and catalogs of all the bands have been made open to the public on 2004 October 1 on the SDF project website.1
A Survey of Compact Star Clusters in the South-West Field of the M 31 Disk
Authors: Kodaira Keiichi , Vansevicius Vladas , Bridzius Audrius , Komiyama Yutaka , Miyazaki Satoshi , Stonkute Rima , Šableviciute Ieva , Narbutis Donatas
Published: March 2014

A survey for compact clusters with a dimension of 10 pc order was conducted in an area of about 500 square arc-minutes of the south-west part of the M 31 disk, making use of the high-resolution capability of Suprime-Cam. Photometry in the $B$, $V$, and $R$ broad-bands, and in the $R^{*}$ medium-band centered around H$\alpha$ with varying apertures was carried out for about 1200 targets, which are related to about 300 compact objects detected in the survey. The results for 101 prominent compact objects are presented as photometric catalogues and morphological atlases, separately for samples with and without strong $\mathrm{H}\alpha$ emission. Many of the compact objects, which were previously suspected to be globular cluster candidates, are judged to be open clusters based upon their internal structures of sub-arc-second order. The majority of the 49 listed compact non-emission objects, which are restricted to be brighter than $M_V \sim-5$, have colors of $0 < B-V < 1.0$, indicating their nature of massive evolved clusters. In contrast, only about 10% of the 52 listed compact emission objects are brighter than $M_V \sim-5$, probably reflecting the short period of the emission phase and the substantial effects of the circum-stellar extinction. The detection of a few candidates of background galaxies is also reported.
Subaru/HDS Abundances in Three Giant Stars in the Ursa Minor Dwarf Spheroidal Galaxy
Authors: Sadakane Kozo , Arimoto Nobuo , Ikuta Chisato , Aoki Wako , Jablonka Pascale , Tajitsu Akito
Published: March 2014

With the HDS (High Dispersion Spectrograph) on the Subaru Telescope, we obtained high-resolution optical region spectra of three red giant stars (COS 4, COS 82, and COS 347) in the Ursa Minor dwarf spheroidal galaxy. The chemical abundances in these stars were analyzed for 26 elements, including $\alpha$-, iron-peak, and neutron-capture elements. All three stars show low abundances of $\alpha$-elements (Mg, Si, and Ca), and two stars (COS 82 and COS 347) show high abundances of Mn compared to Galactic halo stars of similar metallicity. One star (COS 4) has been confirmed to be very metal deficient ($\mathrm{[Fe/H]} =-2.7$) and found to show anomalously low abundances of Mn, Cu, and Ba. In another star, COS 82 ($\mathrm{[Fe/H]} =-1.5$), we have found a large excess of heavy neutron-capture elements with a general abundance pattern similar to the scaled solar system $r$-process abundance curve. These observational results are rather puzzling: low abundances of $\alpha$-elements and high abundance of Mn seem to suggest a significant contribution of SNe Ia at low metallicity, while there is no hint of an $s$-process (i.e., AGB stars) contribution, even at $\mathrm{[Fe/H]} =-1.5$, suggesting a peculiar nucleosynthetic history of the UMi dSph galaxy.
Dramatic Spectral Evolution of WZ Sagittae during the 2001 Superoutburst
Authors: Nogami Daisaku , Iijima Takashi
Published: March 2014

We carried out optical spectroscopic observations of the most enigmatic dwarf nova, WZ Sge, on 11 nights during the 2001 superoutburst. Our observations covered the period from the initial phase several hours before the maximum to the ninth maximum of the rebrightening phase. The first spectrum shows absorption lines of H i (except for $\mathrm{H}\alpha$), H i, and Na i, as well as emission lines of H ii, C iii /N iii, and $\mathrm{H}\alpha$ in doubly-peaked shapes. The same spectrum shows the emission lines of C iv and N iv, which are the first detection in dwarf novae. The spectral features dramatically changed on various time scales. For example, the peak separations of the emission lines of H i and H ii changed from $\sim 700 \,\mathrm{km} \,\mathrm{s}^{-1}$ to $\sim 1300 \,\mathrm{km} \,\mathrm{s}^{-1}$, and one of the peaks dominated over an orbital period in the genuine-superhump era, but the dominant peak remained interchanged with the orbital phase in the early-superhump era. The lines of H i and H i were in emission at the minima of the rebrightening phase (with no high-excitation lines, nor Na i), while they became in absorption at the maxima. We report on the observational results in detail and their implications concerning the outburst mechanism, two types of superhumps, and the variation of the disk structure.
Detection of Short Fading Episodes in Two Dwarf Novae from VSNET Observations
Authors: Kato Taichi
Published: March 2014

From the observations reported to VSNET, we detected short fading episodes in two dwarf novae, RX And (orbital period 5.0 hr) and SU UMa (orbital period 1.8 hr). The episodes in RX And can be naturally explained as the response to a short-term reduction of the mass-transfer rate. A qualitative comparison with VY Scl-type fading is also discussed. In SU UMa, the same explanation is expected to be more difficult to apply. The viable, but still poorly understood, possibilities include a temporary reduction of the quiescent disk viscosity and a temporary reduction of the mass-transfer rate. If the latter possibility is confirmed, we probably need a different mechanism from that of VY Scl-type stars.
On the Possibility of V4444 Sgr as a Recurrent Nova
Authors: Kato Taichi , Yamaoka Hitoshi , Kiyota Seiichiro
Published: March 2014

V4444 Sgr (Nova Sgr 1999) has recently been suggested to be a possible recurrent nova based on the detection of preexisting dust, which may have been formed in a previous outburst. We examined this possibility using the available outburst observations, including the VSNET observations. We also noticed that this nova was recorded in the OGLE II public photometric database, which covered both preoutburst and late-decline phases. The outburst light curve constructed from these observations showed a plateau phase, particularly in the OGLE II $I$-band light curve, which was followed by a more rapid decline. The light curve resembled those of “fast” recurrent novae and candidates in the presence of the distinct plateau phase. The outburst spectrum and the preoutburst magnitude more resemble those of classical novae, but they do not exclude the possibility of a recurrent nova.
Chandra Observation of the Starburst Galaxy NGC 2146
Authors: Inui Tatsuya , Matsumoto Hironori , Tsuru Takeshi Go , Koyama Katsuji , Matsushita Satoki , Peck Alison B. , Tarchi Andrea
Published: March 2014

We present six monitoring observations of the starburst galaxy NGC 2146 using the Chandra X-ray Observatory. We detected 67 point sources in the field of view of the ACIS-S detector. Six of these sources were Ultra-Luminous X-ray Sources, the brightest of which had a luminosity of $5 \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$. One of them, with a luminosity of $\sim 1 \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$, is coincident with the dynamical center location, which may be a low-luminosity active galactic nucleus. We have produced a table where the positions and main characteristics of the detected sources are reported. A comparison between the positions of the X-ray sources and those detected in NIR or radio indicates no definite counterpart. We have derived a $\log{N} \hbox{--} \log{S}$ relation and a luminosity function. The luminosity function has a slope of 0.71 above a detection limit, which is similar to those found in other starburst galaxies. Diffuse emissions were detected in both soft (0.5–2.0 keV) and hard (2.0–10.0 keV) energy bands. The spectra of the diffuse component were fitted with two (hard and soft) components. The hard power-law component, with a luminosity of $\sim 4\times 10^{39}\,\mathrm{erg} \,\mathrm{s}^{-1}$, is likely to have originated by unresolved point sources.
Nobeyama Millimeter Array Observations of GRB 030329: a Decay of Afterglow with Bumps and Molecular Gas in the Host Galaxy
Authors: Kohno Kotaro , Tosaki Tomoka , Okuda Takeshi , Nakanishi Kohichiro , Kamazaki Takeshi , Muraoka Kazuyuki , Onodera Sachiko , Sofue Yoshiaki , Okumura Sachiko K. , Kuno Nario , Nakai Naomasa , Ohta Kouji , Ishizuki Sumio , Kawabe Ryohei , Kawai Nobuyuki
Published: March 2014

Nobeyama Millimeter Array was used to observe millimeter-wave afterglow of GRB 030329 at 93 GHz and 141 GHz from 2003 April 6 (8.23 days after the burst) to 2003 May 30 (61.97 days). A sensitive search for CO $(J=1 \hbox{--} 0)$ emission/absorption from the host galaxy of GRB 030329 was also carried out. Unresolved millimeter continuum emission at the position of GRB 030329 was detected until 2003 April 21. We found a steep decline of continuum flux ($\propto t^{-2.0}$) during this period, in accord with a previous report. Moreover, our data implies that the decay was accompanied by possible plateaus phases, or bumps, on a time scale of several days. From an integrated spectrum, produced by summing up the data from 2003 April 10 to 2003 May 30, we found a possible emission feature, which could be a redshifted CO $(J=1 \hbox{--} 0)$ line. Its position and redshift coincide well with those of GRB 030329, though further observations are required to confirm the detection. If the emission feature is real, the observed CO flux is $1.4 \pm 0.52 \,\mathrm{Jy} \,\mathrm{km} \,\mathrm{s}^{-1}$, corresponding to a large molecular gas mass of $M(\mathrm{H}_2) > 10^9 \,{{{M}_{\odot}}}$. This implies that the host galaxy, which is optically faint, is highly obscured due to a rich interstellar medium.
Mass-Loss Timescale of Star Clusters in an External Tidal Field. I. Clusters on Circular Orbits
Authors: Tanikawa Ataru , Fukushige Toshiyuki
Published: March 2014

We investigated the evolution of star clusters in a steady external tidal field by means of $N$-body simulations. We followed seven sets of cluster models, whose central concentration and strength of the tidal field are different. We found that the mass-loss timescale due to the escape of stars, $t_\mathrm{mloss}$, and its dependence on the two-body relaxation timescale, $t_\mathrm{rh,i}$, are determined by the strength of the tidal field. The logarithmic slope [$\equiv d\ln(t_\mathrm{mloss})/d\ln(t_\mathrm{rh,i})$] approaches unity for the cluster models in weaker tidal fields. The timescale and the dependence are almost independent of the central concentration for clusters in tidal fields of the same strength. In our results, the scaling found by Baumgardt (2001, MNRAS, 325, 1323) can be seen only in cluster models with moderately strong tidal fields.
The SUBARU Deep Field Project: Lymanα Emitters at a Redshift of 6.6
Authors: Taniguchi Yoshiaki , Ajiki Masaru , Nagao Tohru , Shioya Yasuhiro , Murayama Takashi , Kashikawa Nobunari , Kodaira Keiichi , Kaifu Norio , Ando Hiroyasu , Karoji Hiroshi , Akiyama Masayuki , Aoki Kentaro , Doi Mamoru , Fujita Shinobu S. , Furusawa Hisanori , Hayashino Tomoki , Iwamuro Fumihide , Iye Masanori , Kobayashi Naoto , Kodama Tadayuki , Komiyama Yutaka , Matsuda Yuichi , Miyazaki Satoshi , Mizumoto Yoshihiko , Morokuma Tomoki , Motohara Kentaro , Nariai Kyoji , Ohta Koji , Ohyama Youichi , Okamura Sadanori , Ouchi Masami , Sasaki Toshiyuki , Sato Yasunori , Sekiguchi Kazuhiro , Shimasaku Kazuhiro , Tamura Hajime , Umemura Masayuki , Yamada Toru , Yasuda Naoki , Yoshida Michitoshi
Published: March 2014

We present new results of a deep optical imaging survey using a narrow band filter (NB921) centered at ${\lambda = 9196 \,\mbox{Å}}$ together with $B, V, R, i^\prime$, and $z^\prime$ broadband filters in the sky area of the Subaru Deep Field, which has been promoted as one of legacy programs of the 8.2m Subaru Telescope. We obtained a photometric sample of 58 $\mathrm{Ly}\,\alpha$ emitter candidates at $z \approx 6.5 \hbox{--} 6.6$ among $\sim 180$ strong NB921-excess ($z^\prime-\mathit{NB921} \gt 1.0 z^\prime-\mathit{NB921} > 1.0$) objects together with a color criterion of $i^\prime-z^\prime \gt 1.3 i^\prime-z^\prime > 1.3$. We then obtained optical spectra of 20 objects in our NB921-excess sample, and identified at least nine $\mathrm{Ly}\,\alpha$ emitters at $z \sim 6.5 \hbox{--} 6.6$, including the two emitters reported by Kodaira et al. (2003, PASJ, 55, L17). Since our $\mathrm{Ly}\,\alpha$-emitter candidates are free from strong amplification of gravitational lensing, we are able to discuss their observational properties from a statistical point of view. Based on these new results, we obtained a lower limit of the star-formation rate density of $\rho_\mathrm{SFR} \simeq 5.7 \times 10^{-4} \,h_{0.7} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1} \,\mathrm{Mpc}^{-3}$ at $z \approx 6.6$, being consistent with our previous estimate. We discuss the nature of star-formation activity in galaxies beyond $z=6$.
A Statistical Study of Gamma-Ray Emitting Solar Flares Observed with Yohkoh
Authors: Matsumoto Yukari , Makishima Kazuo , Kotoku Jun’ichi , Yoshimori Masato , Suga Kazuharu , Kosugi Takeo , Masuda Satoshi , Morimoto Kouji
Published: March 2014

Gamma-ray emitting solar flares observed with Yohkoh were analyzed from a statistical viewpoint. The four-band hard X-ray (15–95 keV) photometric data, taken with the Hard X-ray Telescope onboard Yohkoh, were utilized in combination with the spectro-photometric gamma-ray (0.2–30 MeV) data obtained with the Gamma-Ray Spectrometer. The GOES class was also incorporated. Out of 2788 X-ray flares observed from 1991 October to 2001 December, 178 events with strong hard X-ray emission were selected. Among them, 40 flares were further found to show significant gamma-ray emission. A fractal dimension analysis and multi-band color–color plots of the 40 flares suggest that their soft X-ray to MeV gamma-ray spectral energy distributions involve at least four independent parameters. These are: (1) the overall flare size; (2) the relative intensities of the thermal vs. non-thermal signals; (3) the gamma-ray to hard X-ray intensity ratio; and (4) the hard X-ray spectral slope. These results are examined for possible selection effects. Also, the meanings of the third parameter are briefly considered.
Hα StokesV/IFeatures Observed in a Solar Active Region
Authors: Hanaoka Yoichiro
Published: March 2014

We carried out an imaging polarimetry observation of active region NOAA 10596 at 9–11 wavelengths around the $\mathrm{H}\alpha$ line with a ferroelectric liquid-crystal polarimeter during 2004 April 20–26. The latitude of the region was $\mathrm{S8}^{\circ}$, and it passed the central meridian on April 23. On the basis of this observation, the Stokes $V/I$ features of the active region in $\mathrm{H}\alpha$, which are expected to indicate the chromospheric longitudinal magnetic field, were revealed as follows: (1) There is persistent weakening (sometimes reversal) of the Stokes $V/I$ signal at the center of the umbra. This is not due to the actual weakening of the magnetic field strength, but probably due to the peculiarity of the atmospheric structure of the umbral chromosphere. (2) The peak wavelengths of the Stokes $V/I$ profile of the plages and that of the sunspot are systematically different from each other and, therefore, it is difficult to apply the weak-field approximation to estimate the chromospheric magnetic field strength. Both of these results mean that an estimation of the chromospheric magnetic field on the basis of the $\mathrm{H}\alpha$ polarimetry is not straightforward, and that an inversion considering the atmospheric structure in the chromosphere is essentially important.
Lithium Abundances of F-, G-, and K-Type Stars: Profile-Fitting Analysis of the Li I 6708 Doublet
Authors: Takeda Yoichi , Kawanomoto Satoshi
Published: March 2014

An extensive profile-fitting analysis was performed for the Li($+$Fe) 6707–6708 Å feature of nearby 160 F–K dwarfs/subgiants (including 27 planet-host stars) in the Galactic disk ($7000 \,\mathrm{K} \gtrsim T_{\mathrm{eff}} \gtrsim 5000 \,\mathrm{K}, -1 \lesssim \mathrm{[Fe/H]} \lesssim +0.4$), in order to establish the photospheric lithium abundances of these stars. The non-LTE effect (though quantitatively insignificant) was taken into account based on our statistical equilibrium calculations, which were carried out on an adequate grid of models. Our results confirmed most of the interesting observational characteristics revealed by recently published studies, such as the bimodal distribution of the Li abundances for stars at $T_{\mathrm{eff}} \gtrsim 6000 \,\mathrm{K}$, the satisfactory agreement of the upper envelope of the $A(\mathrm{Li})$ vs. $\mathrm{[Fe/H]}$ distribution with the theoretical models, the existence of a positive correlation between $A(\mathrm{Li})$ and the stellar mass, and the tendency of lower lithium abundances of planet-host stars (as compared to stars without planets) at the narrow “transition” region of $5900 \,\mathrm{K} \gtrsim T_{\mathrm{eff}} \gtrsim 5800 \,\mathrm{K}$. The solar Li abundance derived from this analysis is 0.92 ($\mathrm{H} = 12.00$), which is by 0.24 dex lower than the widely referenced standard value of 1.16.
Photospheric CNO Abundances of Solar-Type Stars
Authors: Takeda Yoichi , Honda Satoshi
Published: March 2014

We determined the C, N, and O abundances of 160 nearby F, G, and K dwarfs and subgiants by using spectra obtained with the HIDES spectrograph at Okayama Astrophysical Observatory, with the purposes of (1) establishing the runs of $\mathrm{[C/Fe]}, \mathrm{[N/Fe]}$, and $\mathrm{[O/Fe]}$ for these galactic disk stars in the metallicity range of $-1 \lesssim \mathrm{[Fe/H]} \lesssim +0.4$, (2) searching for any difference in the CNO abundances of planet-host stars as compared to non-planet-host stars, and (3) examining the consistency of the abundances derived from different lines to check the validity of the analysis. The non-LTE effect on the abundance determination was taken into consideration based on our extensive statistical-equilibrium calculations. We confirmed that consistent abundances are mostly accomplished between different lines, and that $\mathrm{[C/Fe]}$ as well as $\mathrm{[O/Fe]}$ progressively increase with a decrease in $\mathrm{[Fe/H]}$ with the slope of the former ($\sim 0.2 \hbox{--} 0.3$) being shallower than the latter ($\sim 0.4 \hbox{--} 0.5$), while $\mathrm{[N/Fe]}$ does not show any clear systematic trend with the metallicity. The $\mathrm{[C/Fe]}, \mathrm{[N/Fe]}$, and $\mathrm{[O/Fe]}$ values of 27 planet-harboring stars (included in our sample of 160 stars) were shown to be practically indistinguishable from those exhibited by non-planet-harboring stars of similar metallicities.
X-Ray Spectra of the Narrow-Line Seyfert 1 Galaxy Ton S180 in Comparison with Galactic Black Holes
Authors: Mio MURASHIMA , Kubota Aya , Makishima Kazuo , Kokubun Motohide , Hong Soojing , Negoro Hitoshi
Published: March 2014

An analysis was made of 0.3–15 keV X-ray spectra of a Narrow-Line Seyfert 1 Galaxy, Ton S180, using archival data from ASCA, RXTE, and XMM-Newton. At energies above 2.5 keV, a power-law with a photon index of $\sim 2.3$ successfully and consistently reproduced the spectra from all of these observatories. Assuming this power-law component to extend toward lower energies, a soft excess, which is one of the most remarkable features of Narrow-Line Seyfert 1 Galaxies, is explained by another power-law multiplied by a thermal cutoff at $\sim 0.4 \,\mathrm{keV}$. Some similarities have been observed between this object and Galactic black hole binaries in very high state, the latter being realized under high accretion rates. Attempts have been made to interpret the soft excess in terms of Comptonization of the disk photons by an electron cloud surrounding the accretion disk, like BHBs in a very high state.
Panoramic Views of Cluster-Scale Assemblies Explored by Subaru Wide-Field Imaging
Authors: Kodama Tadayuki , Tanaka Masayuki , Tamura Takayuki , Yahagi Hideki , Nagashima Masahiro , Tanaka Ichi , Arimoto Nobuo , Futamase Toshifumi , Iye Masanori , Karasawa Yoshikazu , Kashikawa Nobunari , Kawasaki Wataru , Kitayama Tetsu , Matsuhara Hideo , Nakata Fumiaki , Ohashi Takaya , Ohta Kouji , Okamoto Takashi , Okamura Sadanori , Shimasaku Kazuhiro , Suto Yasushi , Tamura Naoyuki , Umetsu Keiichi , Yamada Toru
Published: March 2014

We have started PISCES project; a panoramic imaging and spectroscopic survey of distant clusters on Subaru. It exploits the unique wide-field imaging capability of Suprime-Cam, which provides a $34^{\prime} \times 27^{\prime}$ field of view corresponding to a physical area of $16 \times 13 \,\mathrm{Mpc}^2$ at $z \sim 1$. We plan to target 15 clusters at $0.4 \lesssim z \lesssim 1.3$. We report on our first results concerning the inner structures and large-scale structures of two distant clusters at $z = 0.55$ and 0.83 together with the earlier results on a $z = 0.41$ cluster. The photometric redshift technique has been applied to multi-color data in order to remove most of the foreground/background galaxies so as to isolate the cluster member candidates. We have found large-scale filamentary structures around the clusters, extending out to $\gt 5 \,\mathrm{Mpc}$ from the cores, as well as complex inner structures. The galaxy distributions in the inner regions of the clusters look similar to the X-ray intensity maps, suggesting that most of the optical structures trace physically bound systems. We also compared the structures of the three clusters with those of model clusters in a numerical simulation ($N$-body + semi-analytic model) by parameterising the shapes of the iso-density contours of galaxies, and found a broad agreement. Our results that cluster-scale assembly takes place along filaments during hierarchical clustering need to be confirmed spectroscopically in the near future.
Subaru HDS Transmission Spectroscopy of the Transiting Extrasolar Planet HD 209458b
Authors: Narita Norio , Suto Yasushi , Winn Joshua N. , Turner Edwin L. , Aoki Wako , Leigh Christopher J. , Sato Bun’ei , Tamura Motohide , Yamada Toru
Published: March 2014

We have searched for absorption in several common atomic species due to the atmosphere or exosphere of the transiting extrasolar planet HD 209458b, using high precision optical spectra obtained with the Subaru High Dispersion Spectrograph (HDS). Previously we reported an upper limit on $\mathrm{H}\alpha$ absorption of 0.1% ($3 \,\sigma$) within a 5.1 Å band. Using the same procedure, we now report upper limits on absorption due to the optical transitions of Na D, Li, $\mathrm{H}\alpha$, $\mathrm{H}\beta$, $\mathrm{H}\gamma$, Fe, and Ca. The $3 \,\sigma$ upper limit for each transition is approximately 1% within a 0.3 Å band (the core of the line), and a few tenths of a per cent within a 2 Å band (the full line width). The wide-band results are close to the expected limit due to photon-counting (Poisson) statistics, although in the narrow-band case we have encountered unexplained systematic errors at a few times the Poisson level. These results are consistent with all previously reported detections and upper limits, but are significantly more sensitive.
Solar-Cycle Variation of Magnetic Helicity in Active Regions
Authors: Hagino Masaoki , Sakurai Takashi
Published: March 2014

The hemispheric sign rule of helicity and its long-term variation were studied. The data were obtained from the Solar Flare Telescope at Mitaka and the 65-cm solar telescope at Okayama. The data covered the period of 1983–2001, from the declining phase of solar cycle 21 to the rising phase of cycle 23. Although the hemispheric sign rule of helicity generally holds, we also found significant time variations in the yearly values of helicity during the observation period. The hemispheric sign rule of helicity is satisfied in the solar maximum phase, but may not be so in the solar minimum phase.
Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240
Authors: Nakanishi Kouichiro , Okumura Sachiko K. , Kohno Kotaro , Kawabe Ryohei , Nakagawa Takao
Published: March 2014

High spatial resolution observations of the ${{12\atop} \mathrm{CO}}$ (1–0), HCN(1–0), $\mathrm{HCO}^{\mkern-1.26421mu{+}\mkern-2.52842mu}$(1–0), and ${{13\atop} \mathrm{CO}}$(1–0) molecular lines toward the luminous infrared merger NGC 6240 have been performed using the Nobeyama Millimeter Array and the RAINBOW Interferometer. All of the observed molecular emission lines are concentrated in the region between the double nuclei of the galaxy. However, the distributions of both HCN and $\mathrm{HCO}^{{\mkern-1.26421mu{+}\mkern-2.52842mu}}$ emissions are more compact compared with that of ${{12\atop} \mathrm{CO}}$, and they are not coincident with the star-forming regions. The $\mathrm{HCN} / {{12\atop} \mathrm{CO}}$ line intensity ratio is 0.25; this suggests that most of the molecular gas between the double nuclei is dense. A comparison of the observed high $\mathrm{HCN}/{{13\atop} \mathrm{CO}}$ intensity ratio, 5.9, with large velocity gradient calculations suggests that the molecular gas is dense [$n(\mathrm{H}_2) = 10^{4 \hbox{--} 6} \,\mathrm{cm}^{-3}$] and warm ($T_{\mathrm{kin}} \gt 50 \,\mathrm{K}$$T_{\mathrm{kin}} \gt 50 \,\mathrm{K}$). The observed structure in NGC 6240 may be explained by time evolution of the molecular gas and star formation, which was induced by an almost head-on collision or very close encounter of the two galactic nuclei accompanied with the dense gas and star-forming regions.
Spatially Resolved Spectral Analysis of Vela Shrapnel D
Authors: Katsuda Satoru , Tsunemi Hiroshi
Published: March 2014

The ROSAT all-sky survey discovered several ‘shrapnels’, showing boomerang structures outside the Vela supernova remnant. We observed shrapnel D with the XMM-Newton satellite. There is an X-ray bright ridge structure in our FOV running from north to south. Applying the VNEI model to X-ray spectra of various regions, we find that the plasma in the eastern part from the X-ray ridge is significantly different from that in the western part. The X-ray spectra in the western part can be represented by a single-temperature component. The abundances of heavy elements are almost uniform, whereas they are heavily overabundant, except for Fe; the relative abundances to the solar values are $\mathrm{O} \sim 5, \mathrm{Ne} \sim10 , \mathrm{Mg} \sim 10, \mathrm{Fe} \sim 1$. This indicates that shrapnel D originated from the ejecta of the supernova. We find that the plasma in the eastern part from the ridge consists of two components with different temperatures; the hot component comes from the ejecta, while the cold component comes from the interstellar matter. These two components are considered to be in contact with each other, forming a contact discontinuity. Around the northern part of the contact discontinuity, we find wave-like structures of which the typical scale are comparable with that of the Rayleigh–Taylor instability.
Radio Interferometer Sensitivities for Three Types of Receiving Systems: DSB, SSB, and 2SB Systems
Authors: Iguchi Satoru
Published: March 2014

The purpose of this paper is to study the detection sensitivity suitable to the practical situation for a radio interferometer. For the radio interferometer, the three types of receiving systems are a double-sideband (DSB), a single-sideband (SSB), and a two-single-sideband (2SB) systems. The evaluation of these receiving systems is of significance to explore the best performance for a radio interferometer. In this paper, the signal-to-noise ratios of these three-type receiving systems are newly derived to investigate the performance and key features of each system. We demonstrate the system noise temperatures of SSB, 2SB, and DSB receiving systems by using the ALMA-specification receiver noise temperature and the atmosphere condition measured at the ALMA site, and present the relative sensitivities between the 2SB and DSB receiving systems at the ALMA site. From these results, we recommend the 2SB receiving system for all bands of ALMA.
A Vertical Resonance of g-Mode Oscillations in Warped Disks and QPOs in Low-Mass X-Ray Binaries
Authors: Kato Shoji
Published: March 2014

Resonant oscillations in warped disks are examined in order to explain high-frequency QPOs and horizontal-branch QPOs in low-mass X-ray binaries. Different from our previous work, addressed to the same subjects, we relax in this paper the assumption that the disks are isothermal in the vertical direction. That is, the pressure, density, and temperature are assumed to be distributed in the vertical direction with a polytropic relation, and the polytropic index changes as the disk state changes. By this generalization and by some subsidiaries we can qualitatively explain, within the framework of our resonance model, observed large frequency variations in neutron-star QPOs and little variations in black-hole QPOs. We consider vertical resonances of g-mode oscillations, since they are most appropriate to explain observations.
HETE-2 Localization and Observations of the Gamma-Ray Burst GRB 020813
Authors: Sato Rie , Sakamoto Takanori , Kataoka Jun , Yoshida Atsumasa , Suzuki Motoko , Kotoku Junichi , Urata Yuji , Yamamoto Yoshihisa , Arimoto Makoto , Tamagawa Toru , Shirasaki Yuji , Torii Ken’ichi , Matsuoka Masaru , Nakagawa Yujin , Yamazaki Toru , Tanaka Kaoru , Maetou Miki , Yamauchi Makoto , Takagishi Kunio , Lamb Donald Q. , Atteia Jean-Luc , Vanderspek Roland , Graziani Carlo , Prigozhin Gregory , Villasenor Joel , Jernigan J. Garrett , Crew Geoffrey B. , Hurley Kevin , Ricker George R. , Woosley Stanford E. , Butler Nat , Levine Al , Doty John P. , Donaghy Timothy Q. , Fenimore Edward E. , Galassi Mark , Boer Michel , Dezalay Jean-Pascal , Olive Jean-François , Braga Joao , Manchanda Ravi , Pizzichini Graziella , Kawai Nobuyuki
Published: March 2014

A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17 s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4 min after the burst. In the prompt emission, the burst had a duration of approximately 125 s, and more than four peaks. We analyzed the time-resolved 2–400 keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17–52 s after the burst trigger) shows a depletion of low-energy photons below about 50 keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of “jitter” radiation with the usual synchrotron radiation component.
Primordial Molecular Emission in Population III Galaxies
Authors: Mizusawa Hiromi , Omukai Kazuyuki , Nishi Ryoichi
Published: March 2014

We consider the formation of molecules in primordial prestellar clumps and evaluate the line luminosities to assess detectability by next-generation observational facilities. If the initial $\mathrm{H}_2$ fraction is sufficiently high, HD becomes an important coolant in the clumps. The luminosity from such HD cooling clumps is lower than that from $\mathrm{H}_2$ cooling ones because of the lower temperature ($<100 \,\mathrm{K}$). As for Li reactions, we include the three-body LiH formation approximately. The Li molecular fraction remains very low ($<10^{-3}$) throughout the evolution, owing to the high dissociative reaction rate of $\mathrm{LiH} + \mathrm{H} \rightarrow \mathrm{Li} + \mathrm{H}_2$. LiH does not become an important coolant in any density range. The luminous emission lines from the prestellar cores include $\mathrm{H}_2$ rovibrational lines [1–0 Q(1), 1–0 O(3), 1–0 O(5)] and pure rotational lines [0–0 S(3), 0–0 S(4), 0–0 S(5)]. The next-generation facilities SPICA and JWST are able to detect $\mathrm{H}_2$ emission in a large pre-galactic cloud that forms metal-free stars at a high rate of $\sim 10^3 \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$ at a redshift of $z < 10$. We also derive an analytical expression for the luminosity that reproduces the numerical results.
Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I
Authors: Dobashi Kazuhito , Uehara Hayato , Kandori Ryo , Sakurai Tohko , Kaiden Masahiro , Umemoto Tomofumi , Sato Fumio
Published: March 2014

We present a quantitative atlas and catalog of dark clouds derived by using the optical database “Digitized Sky Survey I”. Applying a traditional star-count technique to 1043 plates contained in the database, we produced an $A_V$ map covering the entire region in the galactic latitude range $\vert b\vert \le 40^\circ$. The map was drawn at two different angular resolutions of $6'$ and $18'$, and is shown in detail in a series of figures in this paper. Based on the $A_V$ map, we identified 2448 dark clouds and 2841 clumps located inside them. Some physical parameters, such as the position, extent, and optical extinction, were measured for each of the clouds and clumps. We also searched for counterparts among already known dark clouds in the literature. The catalog of dark clouds presented in this paper lists the cloud parameters as well as the counterparts.
Sunspot Gyroresonance Emission at 17 GHz: A Statistical Study
Authors: Vourlidas Angelos , Gary Dale E. , Shibasaki Kiyoto
Published: March 2014

We investigate the sunspot gyroresonance emission at 17 GHz using the synoptic database of the Nobeyama Radioheliograph. Our statistical study is based on full disk observations obtained during the maximum of Cycle 22 (1992–94). We study the center-to-limb variation of the brightness and polarization of the sunspot radio emission and present some cases of polarization reversal. We find that the radio emission is most likely 3rd-harmonic gyroresonance emission arising from 2000 G fields in transition region, or low corona temperatures.
Radiative Flow in a Luminous Disk II
Authors: Fukue Jun
Published: March 2014

Radiatively-driven transfer flow perpendicular to a luminous disk is examined in the subrelativistic regime of $(v/c)^1$, taking into account the gravity of the central object. The flow is assumed to be vertical, and the gas pressure is ignored, while internal heating is assumed to be proportional to the gas density. The basic equations were numerically solved as a function of the optical depth, and the flow velocity, the height, the radiative flux, and the radiation pressure were obtained for a given radius, an initial optical depth, and initial conditions at the flow base (disk “inside”), whereas the mass-loss rate was determined as an eigenvalue of the boundary condition at the flow top (disk “surface”). For sufficiently luminous cases, the flow resembles the case without gravity. For less-luminous cases, however, the flow velocity decreases, and the flow would be impossible due to the existence of gravity in the case that the radiative flux is sufficiently small. Application to a supercritical accretion disk with mass loss is briefly discussed.
Formation of Magnetically Supported Disks during Hard-to-Soft Transitions in Black Hole Accretion Flows
Authors: Machida Mami , Nakamura Kenji E. , Matsumoto Ryoji
Published: March 2014

We carried out three-dimensional global resistive magnetohydrodynamic simulations of the cooling instability in optically thin hot black hole accretion flows by assuming bremsstrahlung cooling. General relativistic effects are simulated using the pseudo-Newtonian potential. The cooling instability grows when the density of the accretion disk becomes sufficiently large. We found that as the instability grows the accretion flow changes from an optically thin, hot, gas pressure-supported state (low/hard state) to a cooler, magnetically supported, quasi-steady state. During this transition, the magnetic pressure exceeds the gas pressure because the disk shrinks in the vertical direction while almost conserving the toroidal magnetic flux. Since further vertical contraction of the disk is suppressed by magnetic pressure, the cool disk stays in an optically thin, spectrally hard state. The magnetically supported disk exists for a time scale much longer than the thermal time scale, and comparable to the accretion time scale. We examined the stability of the magnetically supported disk analytically, assuming that the toroidal magnetic flux is conserved, and found it to be thermally and secularly stable. Our findings may explain why black hole candidates stay in luminous, hard state even when their luminosity exceeds the threshold for the onset of the cooling instability.
A Study of Accelerated Electrons in Solar Flares Using Microwave and X-Ray Observations
Authors: Grechnev Victor V. , Kundu Mukul R. , Nindos Alexander
Published: March 2014

We consider manifestations of accelerated electrons in microwave and hard X-ray emissions from solar flares. To meet our objectives, we discuss two events — those of 1999 March 16 and February 16. The first event is a short-duration burst, while the second is a long-duration event. An analysis of the first event leads to the conclusion that: 1) a seemingly single-loop configuration can actually be a double-loop one, and 2) it is possible that the pitch-angle distribution of the radio-emitting electrons can be anisotropic with practically no non-zero pitch angles. The second event shows seemingly intersecting flaring loops, and the formation of a post-eruptive arcade that can proceed as a series of double-loop interactions. From these and other published results, we conclude that: 1) double-loop configurations can be responsible for flares showing diverse morphologies and time profiles; 2) the pitch-angle distribution of accelerated electrons can be strongly anisotropic, with an excess of small angles, contributing to a rather narrow energy range of the microwave-emitting electrons.
One Solar-Cycle Observations of Prominence Activities Using the Nobeyama Radioheliograph 1992-2004
Authors: Shimojo Masumi , Yokoyama Takaaki , Asai Ayumi , Nakajima Hiroshi , Shibasaki Kiyoto
Published: March 2014

We newly developed a method of limb-event detection for the Nobeyama Radiograph, and show the results over one solar-cycle, 1992 July–2004 December. We detected 785 prominence activities and 31 flares on the limb by this method. We investigated the relationship between the distributions of the prominence activities and the solar cycle. As a result, we found the following facts: 1) The variation in the number of prominence activities is similar to that of sunspots during one solar cycle. 2) There are differences between the peak times of prominence activities and sunspots. 3) The frequency distribution as a function of the magnitude of the prominence activities (the size of activated prominences) at each phase shows a power-law distribution. The power-law index of the distribution does not change, except around the solar minimum. 4) The number of prominence activities has a dependence on the latitude. On the other hand, the average magnitude is independent of the latitude. 5) During the rise phase of the solar cycle, the location of the high-latitude prominence activities migrates to the pole region. 6) After a solar polarity reversal, the location of the prominence activities in the northern hemisphere migrates to the equator. On the other hand, the prominence activities in the southern hemisphere occurred in the high-latitude region until the decay phase of Cycle 23.
Detection of HCOOCH3 toward a Low-Mass Protostar, NGC 1333 IRAS 4B
Authors: Sakai Nami , Sakai Takeshi , Yamamoto Satoshi
Published: March 2014

The rotational spectral lines of methylformate ($\mathrm{HCOOCH}_3$) have been detected toward a low-mass protostar, NGC 1333 IRAS 4B, with the Nobeyama 45 m radio telescope. The column density is derived to be $(7 \hbox{--} 37) \times 10^{15} \,\mathrm{cm}^{-2}$, assuming a source size of $1^{\prime\prime}$ and the range of the excitation temperature to be from 50 K to 200 K. The column density is almost comparable to those found in other low-mass star-forming regions, NGC 1333 IRAS 4A and IRAS 16293$-$2422. The line width of $\mathrm{HCOOCH}_3$ is $(1.0 \hbox{--} 1.2) \,\mathrm{km} \,\mathrm{s}^{-1}$, which is narrower than that of the high-excitation line of $\mathrm{CH}_3\mathrm{OH}$ ($8_{-4} \hbox{--} 9_{-3}$). Since NGC 1333 IRAS 4B is likely to be a very young protostar, $\mathrm{HCOOCH}_3$ appears even in the early stage of protostellar evolution. The spectral lines of $\mathrm{HCOOCH}_3$ could be used as a novel tracer for detecting an onset of star formation.
The Parsec-Scale Jet of PKS 0637−752
Authors: Edwards Philip G. , Piner B. Glenn , Tingay Steven J. , Lovell James E. J. , Kataoka Jun , Ojha Roopesh , Murata Yasuhiro
Published: March 2014

Chandra observations of the quasar PKS 0637$-$752 during its checkout phase resulted in the unexpected detection of a luminous kiloparsec-scale X-ray jet. The apparent superluminal speed of this jet on the parsec-scale, based on two VSOP and four ground-based observations, has proven crucial to understanding the X-ray production in the arcsec-scale jet. We present here for the first time the full details of the ground-based observations used to determine the parsec-scale jet speed, describe the results of a third VSOP observation, and examine the reported jet speed in the light of more recent ground-based VLBI observations. We find some evidence of increased source activity coincident with extrapolated epochs of jet component ejection, although the monitoring of the source is relatively sparse and the ejection epochs are not tightly constrained. We also construct the spectral energy distribution for the nucleus of PKS 0637$-$752 and show that it can be modelled well in terms of a one-zone synchrotron self-Compton model of an electron-positron jet with a Doppler factor of $\sim 10$, consistent with the results of the VLBI observations.
Systematic Bias in an Estimate of the Cluster Mass and the Fluctuation Amplitude from Cluster Abundance Statistics
Authors: Shimizu Mamoru , Kitayama Tetsu , Sasaki Shin , Suto Yasushi
Published: March 2014

We revisit an estimate of the mass fluctuation amplitude, $\sigma_{8}$, from the observational X-ray cluster abundance. In particular, we examine the effect of the systematic difference between the cluster virial mass estimated from the X-ray spectroscopy, $M_\mathrm{vir,\, spec}$, and the true virial mass of the corresponding halo, $M_\mathrm{vir}$. Mazzotta et al. (2004, MNRAS, 354, 10) recently pointed out the possibility that $\alpha_{M} = M_\mathrm{vir,\, spec} / M_\mathrm{vir}$ is systematically lower than unity. We performed a statistical analysis by combining the latest X-ray cluster sample and the improved theoretical models, and found that $\sigma_8 \sim 0.76 \pm 0.01 + 0.50 \, (1-\alpha_{M})$ for $0.5 \le \alpha_{M} \le 1$, where the quoted errors are only statistical. Thus, if $\alpha_{M} \sim 0.7$, the value of $\sigma_8$ from cluster abundance alone is now in better agreement with other cosmological data, including the cosmic microwave background, the galaxy power spectrum and the weak lensing data. The current study also illustrates the importance of possible systematic effects in mapping real clusters to underlying dark halos, which changes the interpretation of cluster abundance statistics.
The Near-Contact Binary RU Ursae Minoris
Authors: Li-Ying Zhu , Sheng-Bang Qian , Fu-Yuan Xiang
Published: March 2014

The near-contact binary RU UMi with an F0-type primary and a K-type secondary was observed in 2003. With the latest version of the Wilson–Devinney code, the photometric elements were computed. The results reveal that RU UMi is a semi-detached system with the secondary component filling its Roche lobe, which should lead to an increase of the period for conservative mass transfer between the two components. However, an orbital period analysis shows that the orbital period of this system undergoes a continuous decrease at a rate of $dP/dt =-1.72 \times 10^{-8} \,\mathrm{d} \,\mathrm{yr}^{-1}$. Therefore, the continuous period decrease may demonstrate that the system is nonconservative. This can result from a combined effect of mass transfer from the secondary component to the primary one and mass and angular momentum loss from the system. With the secular mass and angular momentum losses, RU UMi may evolve from the present short-period near-contact system into an A-type contact binary.
Subaru Near Infrared Coronagraphic Images of T Tauri
Authors: Mayama Satoshi , Tamura Motohide , Hayashi Masahiko , Itoh Yoichi , Fukagawa Misato , Suto Hiroshi , Ishii Miki , Murakawa Koji , Oasa Yumiko , Hayashi Saeko S. , Yamashita Takuya , Morino Junichi , Oya Shin , Naoi Takahiro , Pyo Tae-Soo , Nishikawa Takayuki , Kudo Tomoyuki , Usuda Tomonori , Ando Hiroyasu , Miyama Shoken M. , Kaifu Norio
Published: March 2014

High angular resolution near-infrared (JHK) adaptive optics images of T Tau were obtained with the infrared camera Coronagraphic Imager with Adaptive Optics (CIAO) mounted on the 8.2 m Subaru Telescope in 2002 and 2004. The images resolve a complex circumstellar structure around a multiple system. We resolved T Tau Sa and Sb as well as T Tau N and S. The estimated orbit of T Tau Sb indicates that it is probably bound to T Tau Sa. The $K$ band flux of T Tau S decreased by $\sim 1.7 \,\mathrm{Jy}$ in 2002 November compared with that in 2001 mainly because T Tau Sa became fainter. The arc-like ridge detected in our near-infrared images is consistent with what is seen at visible wavelengths, supporting the interpretation in previous studies that the arc is part of the cavity wall seen relatively pole-on. Halo emission is detected out to $\sim 2^{\prime\prime}$ from T Tau N. This may be light scattered off the common envelope surrounding the T Tauri multiple system.