本田 敏志

Abstract We conducted the time-resolved simultaneous optical spectroscopic and photometric observations of mid-M-dwarf flare stars YZ CMi, EV Lac, and AD Leo. Spectroscopic observations were obtained using Apache Point Observatory 3.5 m and Small and Moderate Aperture Research Telescope System 1.5 m telescopes during 31 nights. Among the 41 detected flares, seven flares showed clear blue wing asymmetries in the Hα line, with various correspondences in flare properties. The duration of the blue wing asymmetries range from 20 minutes to 2.5 hr, including a flare showing the shift from blue to red wing asymmetry. Blue wing asymmetries can be observed during both white-light and candidate non-white-light flares. All of the seven flares showed blue wing asymmetries also in the Hβ line, but there are large varieties on which other chromospheric lines showed blue wing asymmetries. One among the 7 flares was also observed with soft X-ray spectroscopy, which enabled us to estimate the flare magnetic field and length of the flare loop. The line-of-sight velocities of the blueshifted components range from –73 to –122 km s⁻¹. Assuming that the blueshifts were caused by prominence eruptions, the mass of upward-moving plasma was estimated to be 10¹⁵–10¹⁹ g, which are roughly on the relation between flare energy and erupting mass expected from solar coronal mass ejections (CMEs). Although further investigations are necessary for understanding the observed various properties, these possible prominence eruptions on M-dwarfs could evolve into CMEs, assuming the similar acceleration mechanism with solar eruptions.

Abstract We report on the chemical composition of the very metal-poor (VMP; [Fe/H] = −2.9) star LAMOST J1645+4357, which was identified as a red giant having peculiar abundance ratios by Li et al. The standard abundance analysis is carried out for this object and the well-studied metal-poor star HD 122563, which has similar atmospheric parameters. LAMOST J1645+4357 has a remarkable abundance set, highlighted by these features: (1) nitrogen is significantly enhanced ([N/Fe] = +1.4), and the total abundance of C and N is also very high ([(C+N)/Fe] = +0.9); (2) α-elements are overabundant with respect to iron, as generally found in VMP stars; (3) Ti, Sc, Co, and Zn are significantly deficient; (4) Cr and Mn are enhanced compared to most of VMP stars; and (5) Sr and Ba are deficient, and the Sr/Ba ratio ([Sr/Ba] = −1.0) is significantly lower than the value expected for the r-process. The overall abundance pattern of this object from C to Zn is well reproduced by a faint supernova model assuming spherical explosion, except for the excess of Cr and Mn, which requires enhancement of incomplete Si burning or small contributions from a Type Ia or pair-instability supernova. There remains, however, a question as to why the abundance pattern of this star is so unique among VMP stars.

Abstract Starspots and stellar flares are indicators of stellar magnetic activity. The magnetic energy stored around spots is thought to be the origin of flares, but the connection is not completely understood. To investigate the relation between spot locations deduced from light curves and the occurrence of flares therein, we perform starspot modeling for the TESS light curves of three M-dwarf flare stars, AU Mic, YZ CMi, and EV Lac, using the code implemented in Paper I. The code enables us to deduce multiple stellar/spot parameters by the adaptive parallel tempering algorithm efficiently. We find that flare occurrence frequency is not necessarily correlated with the rotation phases of the light curve for each star. The result of starspot modeling shows that any spot is always visible to the line of sight in all phases, and we suggest that this can be one of the reasons why there is no or low correlation between rotation phases and flare frequency. In addition, the amplitude and shape of the light curve for AU Mic and YZ CMi have varied in two years between different TESS cycles. The result of starspot modeling suggests that this can be explained by the variations of spot size and latitude.

Abstract Stellar coronal mass ejections (CMEs) have recently received much attention for their impacts on exoplanets and stellar evolution. Detecting prominence eruptions, the initial phase of CMEs, as the blueshifted excess component of Balmer lines is a technique to capture stellar CMEs. However, most of prominence eruptions identified thus far have been slow and less than the surface escape velocity. Therefore, whether these eruptions were developing into CMEs remained unknown. In this study, we conducted simultaneous optical photometric observations with Transiting Exoplanet Survey Satellite and optical spectroscopic observations with the 3.8 m Seimei Telescope for the RS CVn-type star V1355 Orionis that frequently produces large-scale superflares. We detected a superflare releasing 7.0 × 10³⁵ erg. In the early stage of this flare, a blueshifted excess component of Hα extending its velocity up to 760–1690 km s⁻¹ was observed and thought to originate from prominence eruptions. The velocity greatly exceeds the escape velocity (i.e., ∼350 km s⁻¹), which provides important evidence that stellar prominence eruptions can develop into CMEs. Furthermore, we found that the prominence is very massive (9.5 × 10¹⁸ g < M < 1.4 × 10²¹ g). These data will clarify whether such events follow existing theories and scaling laws on solar flares and CMEs even when the energy scale far exceeds solar cases.

<jats:title>Abstract</jats:title> <jats:p>Active M-type stars are known to often produce superflares on the surface. Radiation from stellar (super)flares is important for exoplanet habitability, but the mechanisms are not well understood. In this paper, we report simultaneous optical spectroscopic and photometric observations of a stellar superflare on an active M dwarf, YZ Canis Minoris, with the 3.8 m Seimei telescope and the Transiting Exoplanet Survey Satellite. The flare bolometric energy is <jats:inline-formula> <jats:tex-math> <?CDATA ${1.3}_{-0.6}^{+1.6}\times {10}^{34}\,\mathrm{erg}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.6</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>34</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:mi>erg</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacb928ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and the H<jats:italic>α</jats:italic> energy is <jats:inline-formula> <jats:tex-math> <?CDATA ${3.0}_{-0.1}^{+0.1}\times {10}^{32}\,\mathrm{erg}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>3.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>32</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:mi>erg</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjacb928ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The H<jats:italic>α</jats:italic> emission line profile shows red asymmetry throughout the flare, with a duration of 4.6–5.1 hr. The velocity of the red asymmetry is ∼200–500 km s<jats:sup>–1</jats:sup> and the line width of H<jats:italic>α</jats:italic> broadens up to 34 ± 14 Å. The redshifted velocity and line width of H<jats:italic>α</jats:italic> line decay more rapidly than the equivalent width, and their time evolutions are correlated with that of the white-light emission. This indicates the possibility of the white light, the H<jats:italic>α</jats:italic> red asymmetry, and the H<jats:italic>α</jats:italic> line broadening originating from nearly the same site, i.e., the dense chromospheric condensation region, heated by nonthermal electrons. On the other hand, the flux ratio of the redshifted excess components to the central components is enhanced one hr after the flare’s onset. This may be due to the main source of the red asymmetry changing to post-flare loops in the later phase of the flare.</jats:p>

Abstract We present homogeneous abundance analysis of over 20 elements for 385 very metal-poor (VMP) stars based on the LAMOST survey and follow-up observations with the Subaru Telescope. It is the largest high-resolution VMP sample (including 363 new objects) studied by a single program, and the first attempt to accurately determine evolutionary stages for such a large sample based on Gaia parallaxes. The sample covers a wide metallicity range from [Fe/H] ≲ −1.7 down to [Fe/H] ∼ −4.3, including over 110 objects with [Fe/H] ≤ −3.0. The expanded coverage in evolutionary status makes it possible to define the abundance trends respectively for giants and turnoff stars. The newly obtained abundance data confirm most abundance trends found by previous studies, but also provide useful updates and new samples of outliers. The Li plateau is seen in main-sequence turnoff stars with −2.5 &lt; [Fe/H] &lt; −1.7 in our sample, whereas the average Li abundance is clearly lower at lower metallicity. Mg, Si, and Ca are overabundant with respect to Fe, showing decreasing trend with increasing metallicity. Comparisons with chemical evolution models indicate that the overabundance of Ti, Sc, and Co are not well reproduced by current theoretical predictions. Correlations are seen between Sc and α-elements, while Zn shows a detectable correlation only with Ti but not with other α-elements. The fraction of carbon-enhanced stars ([C/Fe] &gt; 0.7) is in the range of 20%–30% for turnoff stars depending on the treatment of objects for which C abundance is not determined, which is much higher than that in giants (∼8%). Twelve Mg-poor stars ([Mg/Fe] &lt; 0.0) have been identified in a wide metallicity range from [Fe/H] ∼ −3.8 through −1.7. Twelve Eu-rich stars ([Eu/Fe] &gt; 1.0) have been discovered in −3.4 &lt; [Fe/H] &lt; −2.0, enlarging the sample of r-process-enhanced stars with relatively high metallicity.

Abstract The chemical abundances of very metal-poor stars provide important constraints on the nucleosynthesis of the first generation of stars and early chemical evolution of the Galaxy. We have obtained high-resolution spectra with the Subaru Telescope for candidates of very metal-poor stars selected with a large survey of Galactic stars carried out with LAMOST. In this series of papers, we report on the elemental abundances of about 400 very metal-poor stars and discuss the kinematics of the sample obtained by combining the radial velocities measured in this study and recent astrometry obtained with Gaia. This paper provides an overview of our survey and follow-up program, and reports radial velocities for the whole sample. We identify seven double-lined spectroscopic binaries from our high-resolution spectra, for which radial velocities of the components are reported. We discuss the frequency of such relatively short-period binaries at very low metallicity.

We present our spectroscopic observations of V455 Andromedae during the 2007 superoutburst. Our observations cover this superoutburst from around the optical peak of the outburst to the post-superoutburst stage. During the early superhump phase, the emission lines of the Balmer series, He i, He ii, Bowen blend, and C iv/N iv blend were detected. The He ii 4686 line exhibited a double-peaked emission profile, where Balmer emission lines were single-peaked, which is unexpected from its high inclination. In the ordinary superhump phase, the Balmer series transitioned to double-peaked emission profiles, and high-ionization lines were significantly weakened. These transitions of the line profiles should be related to the structural transformation of the accretion disk, as expected between the early and ordinary superhump transition in the thermal-tidal instability model. The Doppler map of H alpha during the early superhump phase exhibits a compact blob centered at the primary white dwarf. In analogy to SW Sex-type cataclysmic variables, this feature could emerge from the disk wind and/or the mass accretion column on to the magnetized white dwarf. The Doppler map of He ii 4686 angstrom is dominated by the ring-like structure and imposed two flaring regions with the velocity of similar to 300 km s(-1), which is too slow for a Keplerian accretion disk. The phase of the flaring regions was coincident with the inner spiral arm structure identified during the early superhump phase. Our disk wind model with the enhanced emission from the wind component launched from the inner arm structure successfully reproduced the observed properties of He ii 4686 angstrom. Therefore, V455 And is the first case in dwarf nova outbursts where the presence of the disk wind is inferred from an optical spectrum.

Solar flares are often accompanied by filament/prominence eruptions (similar to 10(4) K and similar to 10(10-11) cm(-3)), sometimes leading to coronal mass ejections that directly affect the Earth's environment(1,2). 'Superflares' are found on some active solar-type (G-type main-sequence) stars(3-5), but the filament eruption-coronal mass ejection association has not been established. Here we show that our optical spectroscopic observation of the young solar-type star EK Draconis reveals evidence for a stellar filament eruption associated with a superflare. This superflare emitted a radiated energy of 2.0 x 10(33) erg, and a blueshifted hydrogen absorption component with a high velocity of -510 km s(-1) was observed shortly afterwards. The temporal changes in the spectra strongly resemble those of solar filament eruptions. Comparing this eruption with solar filament eruptions in terms of the length scale and velocity strongly suggests that a stellar coronal mass ejection occurred. The erupted filament mass of 1.1 x 10(18) g is ten times larger than those of the largest solar coronal mass ejections. The massive filament eruption and an associated coronal mass ejection provide the opportunity to evaluate how they affect the environment of young exoplanets/the young Earth(6) and stellar mass/angular momentum evolution(7).

Young solar-type stars are known to show frequent "superflares," which may severely influence the habitable worlds on young planets via intense radiation and coronal mass ejections. Here we report an optical spectroscopic and photometric observation of a long-duration superflare on the young solar-type star EK Draconis (50-120 Myr age) with the Seimei telescope and Transiting Exoplanet Survey Satellite. The flare energy 2.6 x 10(34) erg and white-light flare duration 2.2 hr are much larger than those of the largest solar flares, and this is the largest superflare on a solar-type star ever detected by optical spectroscopy. The H alpha emission profile shows no significant line asymmetry, meaning no signature of a filament eruption, unlike the only previous detection of a superflare on this star. Also, it did not show significant line broadening, indicating that the nonthermal heating at the flare footpoints is not essential or that the footpoints are behind the limb. The time evolution and duration of the H alpha flare are surprisingly almost the same as those of the white-light flare, which is different from general M-dwarf (super-)flares and solar flares. This unexpected time evolution may suggest that different radiation mechanisms than general solar flares are predominant, such as: (1) radiation from (off-limb) flare loops and (2) re-radiation via radiative back-warming, in both of which the cooling timescales of flare loops could determine the timescales of H alpha and white light.

<jats:title>Abstract</jats:title> <jats:p>Silicon and strontium are key elements to explore the nucleosynthesis and chemical evolution of the Galaxy by measurements of very metal-poor stars. There are, however, only a few useful spectral lines of these elements in the optical range that are measurable for such low-metallicity stars. Here we report on abundances of these two elements determined from near-infrared high-resolution spectra obtained with the Subaru Telescope Infrared Doppler instrument. Si abundances are determined for as many as 26 Si lines for six very and extremely metal-poor stars (−4.0 &lt; [Fe/H] &lt; −1.5), which significantly improves the reliability of the abundance measurements. All six stars, including three carbon-enhanced objects, show over-abundances of Si ([Si/Fe] ∼ +0.5). Two stars with [Fe/H] ∼ −1.5 have relatively small over-abundances. The [Mg/Si] ratios agree with the solar value, except for one metal-poor star with carbon excess. Strontium abundances are determined from the triplet lines for four stars, including two for the first time. The consistency of the Sr abundances determined from near-infrared and optical spectra require further examination from additional observations.</jats:p>

Abstract The Laser Interferometer Gravitational-wave Observatory Scientific Collaboration and Virgo Collaboration (LVC) sent out 56 gravitational-wave (GW) notices during the third observing run (O3). The Japanese Collaboration for Gravitational wave ElectroMagnetic follow-up (J-GEM) performed optical and near-infrared observations to identify and observe an electromagnetic (EM) counterpart. We constructed a web-based system that enabled us to obtain and share information on candidate host galaxies for the counterpart, and the status of our observations. Candidate host galaxies were selected from the GLADE catalog with a weight based on the 3D GW localization map provided by LVC. We conducted galaxy-targeted and wide-field blind surveys, real-time data analysis, and visual inspection of observed galaxies. We performed galaxy-targeted follow-ups to 23 GW events during O3, and the maximum probability covered by our observations reached 9.8$\%$. Among these, we successfully started observations for 10 GW events within 0.5 days after the detection. This result demonstrates that our follow-up observation has the potential to constrain EM radiation models for a merger of binary neutron stars at a distance of up to $\sim$100 Mpc with a probability area of $\leq$ 500 deg$^2$.

Na I. D absorbing systems toward Type Ia supernovae (SNe Ia) have been intensively studied over the last decade with the aim of finding circumstellar material (CSM), which is an indirect probe of the progenitor system. However, it is difficult to deconvolve CSM components from non-variable, and often dominant, components created by interstellar material (ISM). We present a series of high-resolution spectra of SN. Ia. 2014J from before maximum brightness to greater than or similar to 250. days after maximum brightness. The late-time spectrum provides unique information for determining the origin of the Na I. D absorption systems. The deep late-time observation allows us to probe the environment around the SN at a large scale, extending to greater than or similar to 40 pc. We find that a spectrum of diffuse light in the vicinity, but not directly in the line of sight, of the SN has absorbing systems nearly identical to those obtained for the "pure" SN line of sight. Therefore, basically all Na I. D systems seen toward SN. 2014J must originate from foreground material that extends to at least similar to 40 pc in projection and none at the CSM scale. A fluctuation in the column densities at a scale of similar to 20 pc is also identified. After subtracting the diffuse, "background" spectrum, the late-time Na I. D profile along the SN line of sight is consistent with profiles near maximum brightness. The lack of variability on a similar to 1. year timescale is consistent with the ISM interpretation for the gas.

Numerical simulations of structure formation in the early universe predict the formation of some fraction of stars with several hundred solar masses. No clear evidence of supernovae from such very massive stars has, however, yet been found in the chemical compositions of Milky Way stars. We report on an analysis of a very metal-poor star SDSS J001820.5-093939.2, which possesses elemental-abundance ratios that differ significantly from any previously known star. This star exhibits low [alpha-element Fe] ratios and large contrasts between the abundances of odd and even element pairs, such as scandium/titanium and cobalt/nickel. Such features have been predicted by nucleosynthesis models for supernovae of stars more than 140 times as massive as the Sun, suggesting that the mass distribution of first-generation stars might extend to 100 solar masses or larger.

We present the results of our JHKs photometry of asteroid 2012 DA14 at its closest approach to Earth on 2013 February 15. Possible spectral changes associated with resurfacing by planetary encounters are of great interest. The Earth flyby of 2012 DA14 provided a rare opportunity to investigate this effect. Our observations were conducted using the Nishiharima Infrared Camera (NIC) attached to the 2.0 m Nayuta telescope at the Nishi-Harima Astronomical Observatory. Despite the extraordinarily fast sky motion of up to near 50″ s-1, the telescope successfully tracked the asteroid. The NIC achievement of three-band simultaneous observations allowed us to reliably deduce the colors of this fast-moving object. The derived near-infrared relative reflectances are flat, which is consistent with the classification of the asteroid as L-type. The J́-H and H́-Ks colors at 0.5-1 hr after the closest approach are compared with those observed by de León (2013, A&amp A, 555, L2) at́ ∼ 10 hr after the closest time. We did not detect color changes significantly exceeding the photometric errors, which aré ∼ 0.1 mag. This project has demonstrated the potential of the NIC as a three-band simultaneous imager, especially for observations of rapidly time-variable phenomena. © 2014 The Author.

Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10(29) to 10(32) ergs of energy on a timescale of hours(1). Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars(2,3), some of which are rapidly rotating(4,5) and some of which are of ordinary solar type(3,6). The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars(7), but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.

The famous Be/X-ray binary A 0535 + 262/V725 Tau stayed in outburst phase from 2008 to 2011, emitting several X-ray outbursts including the two giant outbursts in November/December 2009 and February 2011. We carried out a high-dispersion spectroscopic monitoring of A 0535 + 262, aiming at the Be disk structure in outburst phase, in particular during outbursts. Our observations could cover the 2009 giant outburst. Observed emission line profiles, reflecting the Be disk structure, showed drastic variabilities. Blue "shoulder" feature in Ha line profile after the periastrons indicates the dense gas stream from the outer part of the Be disk to the neutron star. Other features such as the redshifted enhanced component, the high equivalent width value and the departure from the V/R variabilities suggest that the Be disk had tidally warped component in recent years. We analyzed the radial velocity of the enhanced component and found that the giant outbursts were likely caused by enormous mass transfer from the warped Be disk to the neutron star.

We present the results of an extensive survey of superflares on late-type stars (G, K, and M-type main sequence stars) using the Kepler satellite data. Wefound about 6,800 superflares on late-type stars from the data of about 120,000 stars observed over 500 days. The total bolometric energy of superflares in oursample ranges from 1032 erg to 1036 erg. Our data suggest that the occurrencefrequency of superflares depends on the surface temperature and the rotationperiod of stars. Superflares on M-type stars occur about 10-100 times morefrequently than those on G-type stars. Our results suggest that the average frequency ofsuperflares releasing 10 34-1035 erg of energy (100-1,000 times larger than the largestsolar flares) on M-type stars and Sun-like stars is once in 10 years and once in a few thousand years respectively. Copyright © International Astronomical Union 2014.

We report on optical high-dispersion spectroscopic monitoring observations of the Be/X-ray binary A0535+26/V725 Tau, carried out from 2005 November to 2009 March. The main aim of these monitoring observations is to study spectral variabilities in the Be disc, on both the short (a week or so) and long (more than hundreds of days) time-scales, by taking long-term frequent observations. Our four-year spectroscopic observations indicate that the V/R ratio, i.e. the relative intensity of the violet (V) peak with respect to the red (R) one, of the double-peaked H alpha line profile varies with a period of 500 d. The H beta line profile also varies in phase with the H alpha profile. With these observations covering two full cycles of the V/R variability, we reconstruct the two-dimensional structure of the Be disc by applying the Doppler tomography method to the H alpha and H beta emission-line profiles, using a rigidly rotating frame with the V/R variability period. The resulting disc structure reveals non-axisymmetric features, which can be explained by a one-armed perturbation in the Be disc. It is the first time that an eccentric disc structure is directly detected by using a method other than the interferometric one.

We performed a 1D LTE chemical abundance analysis of an extremely metal-poor star BD+44 degrees 493 ([Fe/H] = -3.7), and set a very low upper limit for its Be abundance A(Be) &lt; -2.0 It may include that the decreasing trend of Be abundances with lower [Fe/H] still holds at [Fe/H] &lt; -3.5, and demonstrate that high C and O abundances do not necessarily imply high Be abundances However, since the star is a subgrant with T-eff similar to 5500K, Be may be depleted

We have determined the isotopic abundance ratio of Li-7/Li-6 in the interstellar media (ISMs) along lines of sight to HD169454 and HD250290 using the High-Dispersion Spectrograph on the Subaru Telescope. We also observed zeta Oph for comparison with previous data. The observed abundance ratios were Li-7/Li-6 = 8.1(-1.8)(+ 3.6) 6.3(-1.7)(+3.0) for HD169454 and HD250290, respectively. These values are in reasonable agreement with those observed previously in the solar neighborhood ISMs within +/- 2 sigma error bars and are also consistent with our measurement of Li-7/Li-6 = 7.1(-1.6)(+ 2.9) for a cloud along the line of sight to. Oph. This is good evidence for homogeneous mixing and instantaneous recycling of the gas component in the Galactic disk. We also discuss several source compositions of Li-7, Galactic cosmic-ray interactions, stellar nucleosynthesis, and big bang nucleosynthesis.

The Japanese Virtual Observatory (JVO) is a web portal for astronomical data and analysis system, and utilizes the standards developed by the IVOA to communicate with the VO-compliant resources in the world. We started official operation of the JVO in March 2008(7) The JVO provides the following web-based services: 1. search for VO-compliant data services in the world, 2. search and access to astronomical data through standard VO interfaces, 3. use of on-line astronomical analysis tools, 4. on-line data reduction for the Subaru telescope, 5. use of data storage on the JVO system. We also operate several VO data services (Sky Node, SIA, SSA) and a publishing registry. As of 22 January 2009 over 1,900 resources in the world are registered to the JVO portal. More than 40,000 pages are requested from the JVO system every month. 1.6 TB of data have been downloaded since the start of the official operation. A GRID computing system was introduced to provide a massive computing resource for reducing the data obtained by the Subaru telescope. In the initial operation, we offer 48 CPU cores, 4 GB memory per core, 1 TB of locally attached hard disk and 100 TB of NFS storage area in the GRID computing system.

We carried out intensive spectroscopic observations of two WZ Sge-type dwarf novae, GIN Lib, and V455 And during their superoutbursts in 2007, at 6 observatories. The observations covered the whole of both superoutbursts from the very maximum to the fading tail. We found evidence of the winds having a speed of similar to 1000 km s(-1) which blew in GW Lib during the rising phase. The evolution of the hydrogen, helium, and carbon lines suggests flaring of the accretion disk and emergence of the temperature inversion layer on the disk.

We present early phase observations in optical and near-infrared wavelengths for the extremely luminous Type Ia supernova (SN Ia) 2009dc. The decline rate of the light curve is Δm15(B) = 0.65 0.03, which is one of the slowest among SNe Ia. The peak V-band absolute magnitude is estimated to be MV = -19.90 0.15mag if no host extinction is assumed. It reaches MV = -20.19 0.19mag if we assume the host extinction of AV = 0.29mag. SN 2009dc belongs to the most luminous class of SNe Ia, like SNe 2003fg and 2006gz. Our JHKs -band photometry shows that this SN is also one of the most luminous SNe Ia in near-infrared wavelengths. We estimate the ejected 56Ni mass of 1.2 0.3 M⊙ for the no host extinction case (and of 1.6 0.4 M⊙ for the host extinction of AV = 0.29mag). The C II λ6580 absorption line remains visible until a week after the maximum brightness, in contrast to its early disappearance in SN 2006gz. The line velocity of Si II λ6355 is about 8000kms-1 around the maximum, being considerably slower than that of SN 2006gz. The velocity of the C II line is similar to or slightly less than that of the Si II line around the maximum. The presence of the carbon line suggests that the thick unburned C+O layer remains after the explosion. Spectropolarimetric observations by Tanaka etal. indicate that the explosion is nearly spherical. These observational facts suggest that SN 2009dc is a super-Chandrasekhar mass SN Ia. © 2009 The American Astronomical Society.

The amount of astronomical data is rapidly growing as the progress of telescope technology and the detection technique of recent years. As a result, the way of traditional analysis is becoming insufficient for utilizing the large amount of data efficiently. The SuprimeCam, which is one of the instruments equipped with the Subaru telescope, has been generating 7 TB of public data since its start of operation. It is almost impossible to transfer all the data to the local machine to analyze them. It is, therefore, desirable to have an environment where the data is analyzed where it is stored. In addition, it is not easy to use the Subaru data for an researcher who is not familiar with the Subaru data reduction. To overcome these difficulties, we developed the server side data analysis system and applied GRID technology to construct the system that carry out multiple jobs on multiple servers. Integrating this system to the Japanese Virtual Observatory, a user can easily utilize the GRID system through the web browser interface. (C) 2007 Elsevier B.V. All rights reserved.

The metallicities and abundance ratios, [ X/ Fe], of 12 elements - C, Na, Mg, Si, S, Ca, Ti, Cr, Ni, Y, Zr, and Ce - are determined for 14 old and 24 young metal-rich stars based on high resolution, high S/ N spectra obtained with the HIDES spectrograph attached to the 1.88 m telescope of Okayama Astrophysical Observatory ( Okayama, Japan). The results show that there is no any significant difference in the [ X/ Fe] versus [ Fe/ H] trend for these elements between the two groups of stars. This is consistent with the kinematics of the two groups of stars being similar to that of the thin disk. In connection with the abundance analysis, we found that iron abundances from Fe II lines are generally higher than those from Fe I lines for cool metal-rich stars. In particular, the [ S/ Fe] ratio strongly depends on stellar temperature. In view of this, the chemical evolution of the element sulfur can only be traced by selecting solar-type stars within a critically narrow temperature range. Inspecting a large sample of metal-rich stars, we found that young metal-rich stars generally have kinematics similar to that of the local thin disk, while old metal-rich stars show two different kinematic distributions, one with VLSR similar to- 10 km s(-1) and the other with V-LSR similar to -50 km s(-1). Abundances of this new population of old metal-rich stars with a slight lag in the Galactic rotation have already been investigated by the present authors. We compared the abundance patterns for the three groups of metal-rich stars, and did not find any significant difference in abundance ratios for the elements investigated. These results indicate an inhomogeneous metallicity enhancement but similar nucleosynthesis history for the Galactic evolution of the thin disk from the beginning to the present.

Virtual Observatory (VO) is an emerging astronomical infrastructure for sharing the astronomical data set in the world. National Astronomical Observatory of Japan (NAOJ) started its VO project (Japanese Virtual Observatory JVO) in 2002, and developed JVO portal prototypes. We have carried out several science use cases, such as cosmic string searches and QSO environment studies, by using the prototype system to examine the functionality of the system. This paper describes a preliminary result of the latter science use case. © 2007 International Astronomical Union.

We present the design and implementation of the Japanese Virtual Observatory (JVO) system. JVO is a portal site to various kinds of astronomical resources distributed all over the world. We have developed five components for constructing the portal: (1) registry, (2) data service., (3) workflow system, (4) data analysis service (5) portal GUI. Registry services are used for publishing and searching data services in the VO, and they are constructed using an OAI-PMH metadata harvesting protocol and a SOAP web service protocol so that VO standard architecture is applied. Data services are developed based on the Astronomical Data Query Language (ADQL) which is an international VO standard and an extension of the standard SQL. The toolkit for building the ADQL-based service is released to the public on the JVO web site. The toolkit also provides the protocol translation from a Simple Image Access Protocol (SIAP) to ADQL protocol, so that both the VO standard service can be constructed using our toolkit. In order to federate the distributed databases and analysis services, we have designed a workflow language which is described in XML and developed execution system of the workflow. We have succeeded to connect to a hundred of data resources of the world as of April 2006. We have applied this system to the study of QSO environment by federating a QSO database, a Subaru Suprim-Cam database, and some analysis services such a SExtractor and HyperZ web services. These experiences are described is this paper.

We present preliminary results on the chemical abundance patterns of extremely metal-poor stars obtained during an ongoing observing program with Subaru/HDS. High-resolution, high signal-to-noise spectra have been obtained for 14 stars with [Fe/H] ≲ -3. Five of them exhibit clear overabundances of carbon, a remarkable characteristic found only in the most metal-poor range. One of the carbon-rich stars, HE 1327-2326, has [Fe/H]NLTE = -5.4, the lowest Fe abundance known. No stars with -5 &lt [Fe/H] &lt -4 have yet been found in our program, suggesting that quite different enrichment processes were responsible for stars with [Fe/H] &lt -5 and [Fe/H] &gt -4. While neutron-capture elements are deficient in most of our stars, one star (BS 16550-087) exhibits large enhancements of its light neutron-capture elements (Sr, Y and Zr), providing a strong constraint on models for the production of such elements in the very early Galaxy. © 2005 International Astronomical Union.

The LTE abundances of sulfur (S) of 21 metal-poor stars and one normal star were explored in the metallicity range of -3 &lt [Fe/H] ≤ 0, based on the equivalent widths of the S I (6) 9212, 9237 Å and S I (6) 8693, 9894 Å lines measured on high-resolution spectra, which were observed by the OAO 1.88-m telescope equipped with HIDES. Our main results are: (1) The abundances derived from the S I (6) lines are consistent with those from the S I (1) lines among our sample stars in the range of [Fe/H] &gt -2 with an average difference of +0.03±0.05 dex, whereas a significant discrepancy is observed in the range of [Fe/H] ≤ -2. (2) The behavior of [S(6)/Fe] versus [Fe/H] of our halo sample stars exhibits a nearly flat trend with an average of +0.62±0.09 dex in the range of -3 &lt [Fe/H] &lt -1.25, and shows a distribution around +0.29 dex in -1.25 ≤ [Fe/H] ≤ -0.7. Our sample stars with -1.25 ≤ [Fe/H] ≤ -0.5 follow an increasing trend with decreasing [Fe/H]. The behavior of [S(1)/Fe] of our sample stars also shows essentially the same trend as [S(6)/Fe], though it is quantitatively different. (3) The S behavior in the range of -3 &lt [Fe/H] ≤ 0 inferred from the abundances of multiplets 6 and 1 are qualitatively consistent with each other, and may be represented by a combination of a nearly flat trend and a linearly increasing trend with decreasing [Fe/H]. A transition of the trend is likely to occur at [Fe/H] ∼ -1.5 dex. © 2005. Astronomical Society of Japan.

We describe the architecture of the Japanese Virtual Observatory (JVO) prototype system version 2. JVO aims at seamless access to astronomical data archives stored in distributed data servers as well as data analysis environment. For this purpose, it is important to establish a framework for access to remote servers, including remote procedure calls (RPCs) and data transfer. A data request for distributed database is described in the JVO Query Language. The JVO system parses the query language and decomposes it into individual remote procedures, such as the retrieval of catalog images and spectra, cross matching, and workflow generation. Based on this workflow, remote procedures are called. For RPCs of JVO prototype system 1, we employed Globus toolkit 2 (GT2). However, latency time of GT2 RPCs was too long for successive short-time jobs. Therefore, we employed Globus toolkit 3 (GT3) for JVO prototype system 2. As a result, we find that Grid Service in GT3 improves performance of RPC. In addition to Grid Service, Reliable File Transfer (RFT) is used for efficient data transfer. Astronomical data stored in distributed servers are discovered through a registry server which provides metadata discussed in the IVOA registry working group and is built using a XML database.

This paper describes a method to search for cosmic strings using their unique gravitational effect, and its implementation to the Japanese Virtual Observatory (JVO). Grand unified theory predicts that super-heavy cosmic strings with linear mass density of 10(22) g/cm were produced at a phase transition in the early universe. The lensing effect by a long straight object can be characterized by undistorted double images which are almost co-aligned in a direction of the string network and distributed in a very large scale. Because of its large scale nature, wide field deep survey is crucial for its discovery, and also the automatic detection system is required to survey the large amount of deep sky data. We have constructed databases of Subaru Suprime-Carn catalog/image for selected areas and applied our search method on the JVO prototype.

The Japanese Virtual Observatory (JVO) project has been conducted by the National Astronomical Observatory of Japan (NAOJ). JVO aims at providing easy access to federated astronomical databases (especially SUBARU, Nobeyama and ALMA) and data analysis environment using the Grid technology. We defined JVOQL (JVO Query Language) for efficient retrieval of astronomical data from a federated database. We then constructed the first version of the JVO prototype in order to study technical feasibility including functionality of JVOQL, remote operations using Globus toolkit. The prototype consists of several components as follows: JVO portal to accept users' requests described in JVOQL, JVO Controller to parse them into individual query requests, and distributed database servers containing Suprime-Cam data of the Subaru telescope and 2MASS data. We confirmed that this prototype actually worked to access to a federated database. We construct the second version of the JVO prototype system to improve usability, which includes new user interfaces, efficient remote operations, and introduction of analysis tools. In the course of this, Grid service and XML database is employed. In this presentation we describe its design and structure of the new JVO prototype system.

A detailed abundance analysis has been carried out for the Hg-Mn star 46 Aql using high-resolution spectra in the visual region (5100-6400 Å) obtained with the High Dispersion Spectrograph of the Subaru Telescope. Our attention has been mainly focused on those elements which have not been analyzed previously. He, C, N, and O are underabundant, while Na shows the solar abundance. We have confirmed previously reported underabundances of Mg, Al, and Si, and have found an overabundances of P (+1.5dex) and Ti (+ 1.0dex) and a significant underabundance of S (-1.8dex). Fe is overabundant by +0.8±0.1 dex and a microturbulent velocity of 0.3kms-1 was found from an analysis of the Fe II lines. Among a few hundred unidentified absorption lines, we identified lines of As II and Xe II and a very large (+4.0dex) overabundance of Xe is obtained. We have confirmed emission lines of Mn II and Ti II near 6100 Å, while those of Cr II cannot have been seen.

We present the results of VRI CCD photometric observations of SS 433 and VRI light-curve modelings for SS 433. Observations were carried out in the fall of 1995 using the 51-cm relfector at Osaka Kyoiku University. Three cycles of the binary phase were covered. The mean magnitudes and colors during the observational periods were V = 14.0, R = 11.1, I = 10.5; V - R = 2.88, V - I = 3.50, R - I = 0.62. On October 17 and 18 a strong flare was observed. Theoretical light curves were also calculated using a model in which SS 433 consists of a geometrically thick torus around a compact star and a companion star filling the Roche lobe. In the torus picture VRI light curves were first calculated; for appropriate parameters VRI model light curves well reproduce the observational profiles. In addition, the extinction was first derived from the magnitude difference between the obervation and the model; A(V) similar to 6-7, A(R) similar to 3-4, and A(I) similar to 3. These values are in good agreement with those of a previous observation.