bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computation of the Adiabatic Eigenmodes of Stars Using the Riccati Method
Authors: Takata Masao , Löffler Wolfgang 
Published: March 2014

Abstract
In stellar oscillation problems, it is often necessary to compute a large number of stellar eigenmodes with wildly varying radial orders and angular degrees. Conventionally the relaxation method is used for this purpose. This method is, however, fraught with several numerical issues, which make it cumbersome and tedious to write the corresponding computer programs. For this reason we adopt the Riccati method as an alternative, in which the original system of linear equations is transformed into a nonlinear matrix Riccati equation. The dependent variable of the converted equation does not retain the dependent variables of the original linear equations themselves, but keeps the relations among them. This method is particularly useful when we compute eigenmodes, where the amplitudes of the eigenfunctions vary by many orders of magnitude, since the ratios of the amplitudes generally show much less variation than the amplitudes themselves. The Riccati method was successfully applied to the problems of nonadiabatic stellar oscillations in previous studies. Our aim is to do the same for the adiabatic case.
Astronomical Observation with a Nb-Al-AlOX-Al-Nb STJ Single Photon Detecor for Optical Wavelengths
Authors: Shiki Shigetomo , Sato Hiromi , Takizawa Yoshiyuki , Kurakado Masahiko , Shimizu Hirohiko M. 
Published: March 2014

Abstract
A test observation using a Nb-Al-$\mathrm{AlO}_{X}$-Al-Nb superconducting tunnel junction detector was carried out using a small commercial optical telescope. Single photons of visible wavelengths were detected from $\alpha$ Lyr, $\alpha$ Boo, and Jupiter, and pulse-height distributions were obtained. The observed spectra roughly agree with predictions.
Low-Ionization Emission-Line Regions around the Nucleus of the Seyfert Galaxy NGC 1068
Authors: Ishigaki Tsuyoshi , Hayashi Tadashi , Ohtani Hiroshi , Sasaki Minoru , Maemura Hiroyuki , Ozaki Shinobu , Hattori Takashi , Sugai Hajime , Ishii Motomi 
Published: March 2014

Abstract
We present the results of tridimensional spectrophotometric observations of the central region of the Seyfert galaxy NGC 1068 obtained by using Kyoto tridimensional spectrograph I. A brief description of the instrument is presented. We have found the existence of low-ionized gas extending out of the ionization cone. It is characterized by higher ([S II]$\lambda6716+\lambda6731) / \mathrm{H}\alpha$ than within the cone. The ratio peaks at $5{}^{\prime\prime} \hbox{--} 6{}^{\prime\prime}$ east and west of the nucleus and reaches to 0.5–0.6. The ionization of the gas outside the cone by the scattered nuclear continuum is examined. We argue that a substantial fraction of the gases outside the cone could be ionized by the scattered nuclear continuum, including the diffuse arc structure seen in an HST image. In addition, we also attempt discussions according to the kinematic and spectroscopic properties of two possible gaseous components derived by the line decomposition: a narrow component that seems to follow the galactic rotation, and a broad one that may be deviated from it.
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

Abstract
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
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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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 $M(\mathrm{H}_2) &gt; 10^9 \,{{{M}_{\odot}}}$. 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

Abstract
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

Abstract
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 ($z^\prime-\mathit{NB921} \gt 1.0 z^\prime-\mathit{NB921} &gt; 1.0$) objects together with a color criterion of $i^\prime-z^\prime \gt 1.3 i^\prime-z^\prime &gt; 1.3$. 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

Abstract
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

AbstractWe 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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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.