The recent development and ongoing observations of the Galaxy Evolution Explorer (GALEX) UV space telescope provide a better understanding of the star formation history in early-type galaxies. Here I will present the recent results of the GALEX observations for the early-type galaxies at 0 < z < 0.2, and discuss the UV upturn phenomenon, recent star formation, and AGN connection.

The VERA (VLBI Exploration of Radio Astrometry) project is the only 10-micro-arcsec scale astrometry observation running currently. Observation series in radio wavelength in 22GHz and 43GHz are performed with 4 radio telescopes in Japan. The aim of VERA is to measure accurate distances, their proper motions and internal motions of radio sources in Galactic star-forming regions and late-type stars. To achieve 10-micro-arcsec accuracy stably the new software with enough numerical accuracy is needed. VEDA (VERA Data Analyzer) is under development for this purpose and the fundamental library for VEDA \"CCcoda\" have been developed. In this seminar current results of VERA are introduced and the structure of CCcoda is described.

지난 5년간 국가그리드사업의 주관기관으로 그리드컴퓨팅 기술개발에 선도적 역할을 수행해 온 한국과학기술정보연구원의 그리드사업 성과 소개 및 고성능컴퓨팅 분야의 대표응용인 기후연구 분야의 연구성과와 향후 계획에 대한 소개

According to the present knowledge, a composition of interstellar absorbing matter is very complex: e.g., the already detected molecules consist of up to 13 atoms and some larger species have already been suggested. Another, perhaps most prominent, evidence of intricate processes of molecular synthesis and destruction taking place in interstellar medium is the existence of diffuse interstellar bands (DIBs) - the longest standing unsolved problem in all of spectroscopy. DIBs were discovered as long ago as in 1921 (Heger) but their carriers remain unknown despite considerable efforts of astronomers and despite a progress in observational astronomy during last 10-15 years. The list of these spectral lines or bands continues to grow, including more and more weak DIBs and reached now ~300 features. I will tell about the current state of the problem of DIBs identification.

Generation of local oscillator power at Terahertz frequencies with conventional techniques is difficult and expensive. In this thesis, I demonstrate steps towards a THz source using the photonic local oscillator technique for submillimeter astronomy. An LT-GaAs photomixer illuminated by two laser signals generates a beat frequency through photoconductive mixing, equal to the difference of two laser frequencies which can be tuned from a few hundred GHz to around a few THz. To generate two frequencies in the same laser for a photonic LO, I have investigated the use of a Ti:Sapphire ring cavity laser. To generate dual-mode operation in the multi-mode laser, two intracavity solid Fabry- Perot etalons were installed. To characterize the spectral width of the photomixing product, the beat frequency was monitored with a commercial photodetector at 34 GHz. The spectral width of the beat frequency was less than 10 kHz. The output power from the LT-GaAs photomixer was found to increase linearly with the applied bias voltage. Unexpectedly large fluctuations in the output power were measured, due to dual-mode intensity variations from the Ti:Sapphire ring cavity laser. The reasons for these power fluctuations are thermal variations of the resonator cavity, mechanical variations, dust particles, air fluctuations, and mode competition. To reduce these power fluctuations, a power stabilization system using volume holographic gratings (VHGs) was developed, which greatly reduced the power fluctuations. I helped develop a 460/810 GHz dual-channel receiver, called the First Light APEX Submillimeter Heterodyne instrument (FLASH), for the Atacama Pathfinder Experiment (APEX) telescope located at Llano de Chajnantor in Chile0s Atacama desert. Using FLASH and the APEX-2A receivers, a large number of molecular transitions toward the Long Period Variable (LPV) star IK Tau were observed. Thirty four transitions of 12 molecular species, including maser lines, were detected. To determine the spatial distribution of the 12CO(3−2) emission, mapping observations were performed. Assuming local thermodynamic equilibrium (LTE), the rotational temperatures of molecules and the molecular abundances were obtained. By comparing the abundance of the individual molecules to those reported in the literature, we found an improvement over previously available observed abundances. To constrain the physical conditions in the circumstellar envelope, emission from the SO2 and CO molecules was modeled using a Monte Carlo method. From the model fits we could estimate the molecular column density and the kinetic temperature of the envelope.

In this talk, I would like to summarize recent works on the spin of the stellar mass black holes. The possible connection between the spin of black holes and explosive phenomena, such as Gamma-ray Bursts and Hypernovae, will be discussed. Ironically, spinning black holes are the sources of the most energetic explosions in the Universe after Big-Bang.

High resolution imaging observations using Chandra X-ray Observatory revealed that there is a large population of point sources in external galaxies. Most of them are believed to be X-ray binaries in galaxies. Low Mass X-ray Binaries (LMXBs) are the subsef of X-ray binary population with low-mass (typically < 1Msun) companions indicating old stellar populations in galaxies. A study of globular clusters (GCs) in external galaxies highlighted extragalactic astronomy for last a few decades. Color distribution, radial/spatial distribution and metallicity distributition of GCs in a galaxy have been used to understand the formation and evolution of a galaxy. In a dynamical point of view GCs are probable birth-place of compact binary later to be observed as X-ray binary. I will present recent studies based on both X-ray and optical observations regarding the LMXBs in external galaxies with a particular interest on theirs connection to globular cluster system in galaxies. The possible formation process for LMXBs will be discussed.

Magnetic reconnection at the dayside magnetopause is dominantly affected by the relative orientation of the magnetic fields in the magnetosheath and magnetosphere, the relative perpendicular velocities of field lines both before and after reconnection, and the location of the minimum geomagnetic field. We have performed a high-resolution and time-dependent three dimensional MHD simulation of interaction between the solar wind and the Earth’s magnetosphere when the dipole tilt, and By and Bz components of the IMF are simultaneously included in the whole volume of the simulation box. In the recent study of Park et al. (2006) found that for positive dipole tilt (northern hemisphere is summer) and southward IMF (Bz = 5 nT, By = 5nT), the reconnection site shifts sunward and equatorward in the summer hemisphere, and moves tailward and away from equator in the winter hemisphere. The dipole tilt creates asymmetry that strongly affects the direction of the plasma flow due to reconnection. Moreover, the electric field in the northern \\\"reconnection\\\" region (antiparallel region) is 50% larger than that at the magnetic equator and twice that at the subsolar point. In present study, for the case of positive dipole tilt, and during the northward IMF (Bz = 5 nT, By = 5nT), magnetic reconnection occurs at high latitudes in the northern dusk due to antiparallel field condition in the summer hemisphere for By > 0 and creates open field lines. The open field lines which are generated in the dusk sector and their feet are on the northern ionosphere, move from dusk to dawn in the dayside magnetopause and then come back to dusk in the tail. Tail reconnection successively occurs in the slant and elevated plasma sheet. The polar cap potential in dusk cell is larger than that the dawn cell in summer hemisphere. Moreover three-cell pattern appears in the northern ionosphere. On the other hand, the negative potential is comparable to the positive potential in winter hemisphere and the distorted three-cell pattern appears in the southern ionosphere. The open-closed boundary in the winter hemisphere appears at higher latitude than that in the summer hemisphere.

In galactic disks, the one dimensional velocity dispersion of interstellar gas is observed to vary between 12-15 km/s in the central parts down to 4-6 km/s in the outer regions. Many physical mechanisms are responsible for generating interstellar turbulence. A prominent one is related to energy feedback from stars particularly in the form of supernova explosions. In this talk, I shall review a number of those mechanisms and using three-dimensional numerical simulations assess the contribution of stellar feedback in the form of supernova explosions to the observed levels of interstellar turbulence at different radii in galactic disks.

High time resolution (> 5 Hz) observations recently opened new opportunities to investigate the tiny space rocks beyond Neptune known as Kuiper Belt Objects. Extensions of such technique will become a valuable tool to discover and characterize rapid optical transients, which have never been properly studied. Another very exciting application of high speed observation is in the area of seeing-damaged image restoration. Digital image signal processing techniques combined with recently developed zero read noise imaging devices can together deliver so called super-resolution images, previously available only through space telescopes. Compared to adaptive optics of high cost and very small field of view, this approach can be an inexpensive alternative and yet cover much larger field of view, making it possible to study dense star fields and detailed galaxy structures from ground observatories.

Dark energy is one of the most mysterious objects in both cosmology and astrophysics today. We introduce and review the current dark energy projects in experimental and theoretical point of view. We also show the future projects to investigate the properties of dark energy.

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The Hayabusa (the original code name is MUSES-C) spacecraft was designed to obtain samples from the surface of an asteroid 25143 Itokawa (1998 SF36) and return them to Earth. Itokawa is classified with S-type asteroid, and its size is 535×294×209 meters. The main objectives of the mission were to demonstrate the performance of various technical items such as autonomous navigation, sampling devices and ion engines. On 12 September 2005, the Hayabusa spacecraft successfully rendezvoused with the target asteroid Itokawa. For nearly two month before the sampling, the remote sensing observations were performed not only for the sampling site selection but also for scientific purposes. In this colloquium, we show the initial scientific results obtained by the multi-band imaging camera (AMICA) [1] [2], that is, its shape, surface topography and mineralogical composition. Unlike previously explored asteroids, this tiny asteroid is covered with numerous boulders instead of fine regolith, and shows large variations in both color and albedo [3]. In addition, we briefly recount a story we experienced in this project. Reference [1] Saito et al. 2006, Science 312, 1341-1344 [2] Yano et al. 2006, Science 312, 1350-1353 [2] Ishiguro et al. 2006, LPSC XXXVII abstract no.1533

We will outline the current status of the Seoul National University Bright Quasar Survey in Optical (SNUQSO). Bright quasars can serve as useful astrophysical tool, but not every bright quasars have been discovered to date. SNUQSO has searched for missing bright quasars in the northern hemisphere as well as at the low galactic latitude region also known as the zone of avoidance. Through our search till June 2006, we have uncovered more than a dozen new bright quasars using Boyunsan Observatory\/s 1.8m telescope. Follow-up optical imaging observations have been undertaken using the SNU\/s newly installed 4k x 4k CCD camera on the Maidanak Observatory\/s 1.5m telescope at sub-arcsec seeing. We will also review preliminary results from the optical imaging observation and the new 4k x 4k CCD camera on the Maidanak Observatory.

The Anglo-Australian Observatory (jointly funded by the UK and Australian governments) has an ongoing technology development and instrumentation program that has yielded forefront astronomical instruments used around the world (e.g. OzPoz on the VLT, 2dF on the AAT). An overview of the current instrumentation projects underway will be presented. This will cover the recently commissioned AAOmega spectrograph (a bench mounted, dual beam spectrograph fed by the fibers from the 2dF positioner), Echidna (a new technology fiber positioner for the FMOS instrument on Subaru), and WFMOS (a very wide-field MOS system for Subaru that was recently explored in a Feasibility Study for Gemini). The Instrument Science group at the AAO is actively involved in exploring and exploiting new technologies applicable to astronomical instrumentation. Studies including development of autonomous pickup relays for multi-object instruments (Starbugs), development of OH suppression in fiber optics, and continued evaluation of other ermging fiber optic technologies are presently underway. An overview of those activities will be given.

The presentation will be in three parts. The first part will be on the “origin of Type II radio bursts without the coronal mass ejections (CMEs)”. There are debates on the origin of type II bursts in the solar corona: (i) flare blast-wave driven and (ii) CME-piston driven. We have made an analysis to check whether there are any type II bursts that can be generated without CMEs. The second part will be on the “relation between the X-ray plasma ejections and type IIs”. The plasma eruptions very close to the sun are observed in X-rays using the satellite Yohkoh. We have studied in detail the association between these X-ray plasma ejections and type IIs. The final part of the presentation will be on some of the recent works in progress.

Star clusters are likely to be formed with initial angular momentum. Dynamical evolution of rotating star clusters has been investigated by the Fokker-Planck method and N-body integration. The rotation is found to accelerate the core collapse as well as the post collapse evolution. The angular momentum is transferred outward through the relaxation process. The computational details and the astrophysical implications of our recent findings will be presented.

Solid State Telescope(SST), one of the four space plasma instruments being developed for STSAT-1, is designed specifically to measure the energetic electrons with energies from 25KeV to 600KeV. With three other plasma instruments, Electro-static Analyzer(ESA), Langmuir Probe(LP), and Scientific Magnetometer(SM), SST allows in-situ detection of penetrating auroral electrons in the polar region and thus, the study of microscale physics with high time resolution data of the earth\\/s polar region that has not been previously achieved with other space missions. As our society increasingly relies on spacecraft operations in the Earth’s magnetosphere, the forecast of the space weather become more significant. Specially, the long-duration (for several days) high intensity fluxes of relativistic electrons (more than MeV energy) have been revealed to affect serious operation failure or damage to spacecrafts and satellites. So many researchers have tried to understand the dynamics of those relativistic electrons: where they come from and how they get so high energy. This work focus on the possibility of substorm injected electrons as seed electrons of relativistic electrons at the inner magnetosphere during magnetic storm time and we tested ULF and whistler chorus wave as one of acceleration mechanisms of relativistic electrons.

남극세종과학기지에서는 1990년부터 3성분 ring core fluxgate 자력계, proton 자력계를 이용하여 지자기장의 변화를 측정해오고 있다. 또한 2006년부터는 절대지자기측정도 병행하고 있다. 현재 세종기지의 지자기 자료는 인공위성과 인터넷을 통해 실시간으로 미국지질조사소로 전송되고 있다. 2007년에는 세계적 지자기 관측망인 INTERMAGNET에도 가입할 예정이다. 세종기지의 지자기 관측은 관측소가 적은 남극에서 그 희소성을 인정받고 있으며, 우주환경변화 연구에도 활용될 수 있을 것이다

Inflation is the most promising candidate to solve various cosmological problems of the big bang cosmology. We start with the motivation of inflation, and briefly review the scenario of cosmological inflation. Then we discuss some incorrectly known subjects on inflation.

Kuiper belt objects (KBOs) are a class of small bodies located beyond 30 AU from the Sun, and Centaur objects are another class of those orbiting mainly between Jupiter and Saturn. With the rapid discovery of growing number each year, over 1,000 KBOs and 60 Centaurs were known to date. Two out of three dwarf planets, which are new class by IAU resolution voted in Prague are the member of KBOs. It is widely believed that they are remnant planetesimals from the early accretion phases of the Solar System and constitute an important reservoir of primitive materials. Centaurs are often speculated to be objects in transition from the Kuiper belt, as their orbits dynamically evolve into Jupiter-family comet orbits or they get ejected from the Solar System. Photometric observations constrain the size, surface albedo, and rotational properties from its lightcurve. The lightcurve is useful to estimate the shape and lower limit of bulk density of the body. The results of several observations of KBOs and Centaurs with 1-m telescope at Wise Observatory and 200-inch telescope at Palomar Observatory will be presented. In particular, detailed results of new Centaur comet 174P/Echeclus will be given. In parallel, I will introduce the thermal model, which solves the energy equation and the mass balance equation numerically. The energy sources of young KBOs taken to be the external heat source from the early Sun and the internal heat source from radioactive species (in particular 26Al) are comparable at the typical distance of KBOs from the Sun (~ 40 AU). The models suggest that KBOs are likely to lose the ices of very volatile species during early evolution and the internal structure of KBOs is most probably not uniform but stratified with the outer layers being less altered by evolution. Additionally, cometary activity was not rare for the orbits of Centaurs and some of scattered KBOs even without radiogenic heating.

1986년 3월 천문학 연구의 활성화 및 천문우주과학의 저변확대라는 명분으로 大統領令에 의해 국가기관인 국립천문대가 폐지됨과 동시에, 민간기관 (정부출연연구소)인 천문우주과학연구소 (현, 한국천문연구원)이 창립되었으며, 우리나라의 천문학뿐만 아니라 우주과학의 비약적인 발전 기틀을 마련할 수 있었었다. 돌이켜 보면 연구기관이 설립된 후 20년 동안, 수많은 우여곡절도 있었지만, 그 동안 모든 연구소 직원들의 노력과 희생정신으로 획기적인 발전을 이루었고, 한국의 천문우주과학계의 발전에 크게 기여해 오고 있었음을 알 수 있다. 2006년인 올해가 연구기관 창립된 지 20년이 되는 이 시점에서, 한국천문연구원의 보다 더 지속적인 발전을 위해, 연구원의 지난 20년간의 발달과정과 성과를 재평가해 보고, 한편으로 21세기의 글로벌 과학기술경쟁시대에, 국가가 절대적으로 필요로 하는, 그리고 첨단 과학기술을 선도하는 천문우주과학 연구기관으로 거듭나기 위해 앞으로의 발전방향을 모색하는 것은 매우 의의 있는 일이라 본다.

A transiting extrasolar planet sequentially blocks off the light coming from the different parts of the disk of the host star in a time dependent manner. Due to the spin of the star, this produces an asymmetric distortion in the line profiles of the stellar spectrum, leading to an apparent anomaly of the radial velocity curves, known as the Rossiter -- McLaughlin effect. We derive approximate but accurate analytic formulae for the anomaly of radial velocity curves taking account of the stellar limb darkening. Then we show the first discovery of the misalgnment angle between the spin axis of the host star and the orbital axis of the planet, HD 209458b. We also describe our recent theoretical modeling of photometric and spectroscopic signatures of rings around transiting extra-solar planets.

KVN(Koeran VLBI Network) is the first VLBI system in Korea and also the first dedicated millimeter wave VLBI in the world. KVN consists of three stations with 21m radio telescopes, such as Seoul (Yonsei Univ.), Ulsan(Ulsan Univ.) and Jeju(Tamna Univ.). In millimeter and sub-millimeter wave observation for VLBI, it is very crucial to correctly calibrate the phase variations of the electromagnetic waves propagating through the troposphere. To overcome this issue, KVN employs unique the multi- frequency bands receiver system which is able to perform the simultaneous observation up to four frequency bands, 22GHz, 43GHz, 86GHz and 129GHz. The phase calibration by using multi-frequency bands receiver system is based on that the phase fluctuations from a given amount of water vapor increase linearly with frequency, that is, the troposphere is non-dispersive in terms of phase fluctuations. The multi-frequency bands receiver system and the current status of KVN will be described.

It is believed that relativistic jets from several kinds of objects in the universe are all formed by violent phenomena near the black holes. Among the proposed mechanisms, the magnetic mechanism of the jet formation becomes most promising because it may explain not only the acceleration but also the collimation of the jets. However, the distinct mechanism has not yet been shown. Here we report numerical results of jet formation driven by magnetic field due to the current loop near a rapidly rotating black hole, based on the general relativistic magnetohydrodynamics (GRMHD). In such magnetic configuration, there are magnetic flux tubes which bridge the region between the ergosphere and the disk around the black hole. We call the magnetic flux tubes `magnetic bridges’. The result clearly shows that the `magnetic bridges\/ between the ergosphere and the disk are not stationary and expand explosively to form a relativistic jet. Furthermore, it suggests that the magnetic reconnection is caused in the expanding magnetic bridges frequently. To study the magnetic reconnection near the black hole, we have to take account of the electric resistivity. The basic method, tests, and the applications of the GRMHD with resistivity are shown.

Main-sequence fitting, also known as the photometric parallax method, has long been used to estimate distances to individual stars and star clusters beyond the limits of parallax studies. However, this approach has been ultimately limited by the accuracy of the isochrones and the availability of the cluster parameters like metallicity and foreground reddening. In this talk I will report the recent effort to improve the accuracy of isochrones by employing empirical corrections to the color-temperature relations. I will show that the distances can be estimated with 2-3% error using the empirically calibrated isochrones, and metallicities with better than 0.1 dex.

High Mass X-ray Binary Pulsars (HMXBP), in which the companion star is a source of supersonic stellar wind, provide a laboratory to probe the velocity profile of such winds. Here, my talk will consist of three parts. In the first part, I will present our measurements of the X-ray spectral evolution over the binary orbit for four HMXBP observed with the Rossi X-ray Timing Explorer and the BeppoSAX satellites. In one pulsar 4U 1538-52, we find the spherically symmetric stellar wind model corroborating the observations, whereas in the other three, the stellar wind seems to be very clumpy. Moreover, in GX 301-2, neither the presence of a disk nor a gas stream from the companion was validated. In the second part, I will present the timing and spectral properties of the transient Be/X-ray binary pulsar 3A 0535+262 during quiescence using three observations with BeppoSAX. We report the detection of pulsations at a very low luminosity of 2 $\\\\times$ 10$^{33}$ erg s$^{-1}$ during one of the three observations, though at this accretion rate the system is expected to be in the centrifugally inhibited regime. The X-ray spectra for the unpulsed observations are best modeled as power law type while a combined model of power law and black-body is required to fit the pulsed spectrum. Lastly, I will report our results on the study of the spectral properties of the HMXBP Cen X-3 and 4U 0114+650 in their high and low states. Thereafter, I will conclude by stating my future research plans.

The high ionization state of the intergalactic medium is maintained by theintergalactic UV background radiation. This ionizing radiation field is supposed to be the integrated radiation of quasars and young star-forming galaxies, which is reprocessed and attenuated by the intergalactic gas. Though the UV background is inaccessible to direct observations, constraints of its spectral energy distribution can be derived from studies of metal absorption systems, the HI Lyman alpha opacity, or the HeII Lyman alpha forest, respectively. Observations of the HeII/HI column density ratio particularly probe the variations of the UV background at redshifts z ~ 2 - 3. Observations of the HeII Lyman alpha forest towards the quasars HE2347-4342 and HS1700+6416 will be presented. The main results indicate that the UV background is strongly fluctuating on 1 Mpc scales and the hardness of the ionizing radiation seems to be correlated with the density of the absorbing material. However, it can be shown that these results may be affected, at least partly, by the applied analysis method. The caveats of the standard procedures will be discussed and an alternative approach is suggested which takes into account the thermal state of the intergalactic medium.