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Publications of The Korean Astronomical Society
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The Korean Astronomical Society
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Volume 20, Issue 1 - Dec 2005
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MOLECULAR LINE STUDY OF L1014 WITH SRAO 6M TELESCOPE
Lee, Chang-Won ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 1~5
DOI : 10.5303/PKAS.2005.20.1.001
We report molecular line observations of CO(1-0),
, CS(2-1), and HCN(1-0) with SRAO 6m telescope toward L1014-IRS which is thought to be a very faint infrared source embedded in previously known 'starless' core L1014. The CO(1-0) observations find several components with different velocities along the line of sight of L1014,
. We find a parsec scale CO molecular outflow at the
component for the first time the direction of which is coincident with that of the small scale (
) outflow previously found. Although the observation is not covered for whole area of the outflow, the size of the molecular outflow seems not very inconsistent with the expected age of L1014-IRS. More accurate size and shape of the molecular outflow from L1014-IRS will be determined from the full coverage mapping in CO over the outflow region in very near future.
MODEL CALCULATIONS OF THE UV - EXCITED MOLECULAR HYDROGEN IN INTERSTELLAR CLOUDS
Lee, Dae-Hee ; Pak, Soo-Jong ; Seon, Kwang-Il ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 7~10
DOI : 10.5303/PKAS.2005.20.1.007
We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level
according to the combinations of five physical conditions: the input UV intensity, the
column density, cloud temperature, total density, and the
formation rate efficiency. The models include the populations of all the accessible states of
with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of
is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the
molecular fraction, as predicted in theory.
ORFEUS SURVEYS OF THE INTERSTELLAR MOLECULAR HYDROGEN
Lee, Dae-Hee ; Seon, Kwang-Il ; Min, Kyoung-Wook ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 11~20
DOI : 10.5303/PKAS.2005.20.1.011
We present measurements of interstellar
absorption lines in the continuum spectra of 54 early-type stars in the Galactic disk and halo and 3 stars in the Magellanic Clouds. The data were obtained with the Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS), part of the ORFEUS telescope, which flew on the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The spectra extend from the interstellar cutoff at
with a spectral resolution of
and statistical signal-to-noise ratios between 10 and 65. Assuming a velocity profile derived from optical observations (when available), we model the column densities N(J) of the rotational levels J = 0 through 5 for each line of sight. Our data reproduce the relationships among molecular and total hydrogen column density, fractional molecular abundance, and reddening first seen in Copernicusobservations of nearby stars (Savage et al. 1977). The results show that most of these molecular clouds have
total column densities between
, and kinetic temperatures from 21 K to 232 K, with average of 89 K, consistent with the result of Copernicus (Savage et al. 1977).
SHORT-PERIOD VARIABILITY SURVEY (SPVS) IN BOAO
Jeon, Young-Beom ; Kim, Seung-Lee ; Park, Yoon-Ho ; Park, Byeong-Gon ; LeeK, Chung-Uk ; Lee, Eun-Jeong ; Kim, Min-Su ; Lee, Kyung-Hoon ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 21~27
DOI : 10.5303/PKAS.2005.20.1.021
We have been performing a wide-field photometric monitoring program, named SPVS (Short-Period Variability Survey), at the Bohyunsan Optical Astronomy Observatory (BOAO). The observation system consists of a small refracting telescope (D = 155 mm, f = 1050 mm) and a
CCD Camera. The field of view is
. Detection limit is about V = 13 for short-period small amplitude variables such as
Scuti-type pulsating stars, and about V = 15 for long-period large amplitude variables such as eclipsing binaries and RR Lyrae stars. The instrument is designed to be remote-controlled through internet. The primary purpose of this project is to search for variable objects in bright Galactic open clusters. We present results of test observations conducted towards NGC 7092.
NEW VARIABLE STARS AROUND THE CEPHEID VARIABLE TU CAS
Jeon, Young-Beom ; Park, Yoon-Ho ; Nam, Ki-Hyung ; Lee, Kyung-Hoon ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 29~35
DOI : 10.5303/PKAS.2005.20.1.029
Time-series observations were carried out using a 155mm refractor and a
CCD camera at Bohyunsan Optical Astronomy Observatory. We found 38 new variable stars in the
region around the Cepheid variable TU Cas: 22 eclipsing binary stars, 11
Scuti type stars and an RR Lyrae star, and 4 unclassified variables.
UNDERSTANDING OF DISK STRUCTURE DURING THE COLLAPSE OF THE VISCOUS DISK USING SELF-SIMILAR AND NUMERICAL SOLUTIONS
Yoo, Kye-Hwa ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 37~42
DOI : 10.5303/PKAS.2005.20.1.037
The problem for the collapse of isothermal and rotational self-gravitational viscous disk is considered. We derive self-similar solutions for the cases in the inner and outer regions of the self-gravitational viscous disk. We show that surface density depends on
in the outer region of the disk using a slow accretion approximation. The ratio of a modified viscous parameter in the outer region of the disk to that in the inner region is 0.042. We resorted to numerical solutions of governing equations of the self-gravitational disk to find out profiles of
, u and
in terms of x. Their profiles were rapidly changed around the innermost region of the self-gravitational disk. It indicates that a new object was formed in the most inner region of the disk.
THE HIGH RESOLUTION SPECTRA OF PU VUL IN 2004 - I
Yoo, Kye-Hwa ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 43~48
DOI : 10.5303/PKAS.2005.20.1.043
We present a high resolution spectrum of PU Vul observed at Bohyunsan Optical Astronomy Observatory (BOAO) on April 9, 2004. Permitted emission and nebular lines of PU Vul had been significantly changed compared to all spectra observed since its eruption in 1979. Therefore all new lines should be re-identified and were done so. We do-convoluted a
line into several emission components with Gaussian functions. Then we carefully discussed the geometrical feature of PU Vul in April 2004.
INTENSITY ESTIMATION OF WEAK EMISSION LINES
Seon, Kwang-Il ; Lee, Dae-Hee ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 49~53
DOI : 10.5303/PKAS.2005.20.1.049
We are often faced with the task of having to estimate the amplitude of a source signal in the presence of a background. In the simplest case, the background can be taken as being flat, and of unknown magnitude B, and the source signal of interest assumed to be the amplitude A of a peak of known shape and position. We present a robust method to find the most probable values of A and B by applying the one-dimensional Newton-Raphson method. In the derivation of the formula, we adopted the Bayesian statistics and assmumed Poisson distribution so that the results could be applied to the analysis of very weak signals, as observed in FIMS (Far-ultraviolet IMaging Spectrogaph).
CONSTRUCTION OF DATABASE FOR THE DIGITIZED SKY SURVEY I DATA
Sung, Hyun-Il ; Sang, Jian ; Kim, Sang-Chul ; Kim, Bong-Gyu ; Yim, In-Sung ; Ahn, Young-Suk ; Sohn, Sang-Mo-Tony ; Yang, Hong-Jin ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 55~62
DOI : 10.5303/PKAS.2005.20.1.055
The First Generation Digitized Sky Survey (DSS-I) is a collection of digitized photographic atlases of the night sky taken from the Palomar Observatory (northen sky) and the Anglo-Australian Observatory (southern sky). DSS-I is widely used by the astronomical community for a number of applications including object cross-identification and astrometry. However, accessing and retrieving the actual images are nontrivial owing to the huge size (> 60 GB) of the dataset. To facilitate retrieval process of DSS-I data for the public, Korean Astronomical Data Center (KADC) developed a web application that provides not only data retrieval but also visualization functions. The web application consists of several modules developed using Java Applet, Jave Servlet, and JaveServer Pages (JSP) technologies. It allows users to retrieve images efficiently in various formats such as FITS, JPEG, GIF, and TIFF, and also offers an interactive visulization tool, ImgViewer, for displaying/analyzing FITS images. To use the web application, users require a Java-enabled web browser.
THE DESIGN OF NETWORK MODEL FOR THE IMPLEMENTATION OF e-VLBI
Song, Min-Gyu ; Byun, Do-Young ; Kim, Hyun-Goo ; Oh, Se-Jin ; Han, Seog-Tae ; Roh, Duk-Gyoo ; Lee, Bo-Ahn ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 63~71
DOI : 10.5303/PKAS.2005.20.1.063
e-VLBI was invented to enhance the efficiency of VLBI (Very-Long-Baseline Interferometry) system by transmitting the data via high speed network. Korean VLBI Network (KVN) has a plan to construct e-VLBI system named e-KVN. High speed backbone network and efficient network model are essential to implement successful e-VLBI system. This paper introduces a network model based on PC cluster technology. The present status of high speed backbone network in Korea is overviewed. We suggest that the network link via Korea Advanced Research Network (KOREN) is one of feasible way for e-KVN. We also describe the principles of e-VLBI and protocol for network transmission such as VSI-E (VLBI Standard Interface - Electronic), RTP (Real-Time Transport Protocol) and RTCP (Real-Time Transport Control protocol).
DEVELOPMENT OF ON-THE-FLY(OTF) OBSERVATION METHOD FOR SEOUL RADIO ASTRONOMY OBSERVATORY(SRAO) 6-METER TELESCOPE
Kang, Hyun-Woo ; Byun, Do-Young ; Park, Yong-Sun ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 73~83
DOI : 10.5303/PKAS.2005.20.1.073
On-The-Fly (OTF) observation method is developed for the efficient use of 6 M radio telescope at Seoul Radio Astronomy Observatory (SRAO). This technique, in which data and information of antenna position are recorded synchronously while driving a telescope regularly and rapidly across a field, provides more efficient use of telescope time and better calibration of the acquired data than the traditional point-to-point observation method does. For the realization of the method, we (1) added RT-Linux modules to the existing operating system, (2) replaced digital voltmeter with voltage-to-frequency converter, and (3) modified many SRAO observation programs. By observing Moon and G78.2+2.7 using this method and comparing them with previous observations, we verify the successful operation and efficiency of the OTF observation mode.
JAVA BASED WEB APPLICATION FOR THE ASTRONOMICAL CATALOGUES
Sung, Hyun-Il ; Sang, Jian ; Kim, Bong-Gyu ; Yim, In-Sung ; Kim, Sang-Chul ; Ahn, Young-Suk ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 85~95
DOI : 10.5303/PKAS.2005.20.1.085
We collected eleven large astronomical catalogues, which include 2MASS, USNO B1.0, GSC 2 catalogues and so on. Most of these catalogues are the frequently used by astronomers for all sorts of applications. But the researches are faced with the problem of accessing these databases because these catalogues contain from tens millions up to thousands of millions of records. So we developed a web application system to manage these large catalogues, the main purpose of the web application is to allow a powerful and efficient querying activity on these catalogues through internet by using a simple web interface. User could retrieve the query result in variety of formats including plain text, HTML, Microsoft Excel format (XLS), and VOTable. Furthermore, user also could display and analyze result graphically by using a powerful interactive visualization tools named VOPlot which was developed by the Virtual Observatory-India (VOI) project.
DEVELOPMENT OF AN AUTOMATIC PROCESSING PROGRAM FOR BOES DATA
Kang, Dong-Il ; Park, Hong-Suh ; Han, In-Woo ; Valyavin, G. ; Lee, Byeong-Cheol ; Kim, Kang-Min ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 97~107
DOI : 10.5303/PKAS.2005.20.1.097
We developed a data reduction program (RX) to process BOES data automatically. It processes a whole set of data taken during one night automatically - preprocessing, extraction to one-dimensional spectra and wavelength calibration. The execution is very fast and the performance looks pretty good. We described the performance of this program, comparing its procedure with that of IRAF. RX does not have functions for continuum normalization yet. We will develop those functions in the next works.
ON THE BACKGROUND-SUBTRACTED INTENSITY
Seon, Kwang-Il ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 109~116
DOI : 10.5303/PKAS.2005.20.1.109
When we measure a source signal in the presence of a background rate that has been independently measured, the usual approach is to obtain an estimate of the background rate by observing an empty part of the sky, and an estimate of the source signal plus background rate by observing the region where a source signal is expected. The source signal rate is then estimated by subtracting the background rate from the source signal plus background rate. However, when the rates or their observation times are small, this procedure can lead to negative estimates of the source signal rate, even when it should produce a positive value. By applying the Bayesian approach, we solve the problem and prove that the most probable value of source signal rate is zero when the observed total count is smaller than the expected background counts. It is also shown that the results from the conventional method is consistent with the most probable value obtained from the Bayesian approach when the source signal is large or the observation time is long enough.
CONCEPTUAL DESIGN STUDY OF THE BOES STOKESMETER
Kim, Kang-Min ; Han, In-Woo ; Plachinda, S. ; Valyavin, G. ; Yoo, Kye-Hwa ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 117~124
DOI : 10.5303/PKAS.2005.20.1.117
We plan to install the polarimetric optics in the AGU(acqusition and guiding unit) of the 1.8 m telescope at the BOAO(Bohyunsan Optical Astronomy Observatory). With this, the spectropolarimetric observations with the resolution of 45,000 and 60,000 in 4,000 to
ange could be done by the BOES(BOao Echelle Spectrograph). If we use the precision radial velocity measurement capability of the BOES, the accuracy of the magnetic field intensity measurements with this new BOES stokesmeter will be much increased. We present here the design concept of the BOES stokesmeter. Some details on the optics, mechanical parts, fiber parts and the lab test procedures of this stokesmeter are explained.
SMALL-SCALE GIGABIT VLBI OBSERVATION SYSTEM USING PC
Oh, Se-Jin ; Roh, Duk-Gyoo ; Kim, Kwang-Dong ; Chung, Hyun-Soo ; Je, Do-Heung ; Wi, Seog-Oh ; Han, Seog-Tae ; Kim, Hyun-Goo ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 125~134
DOI : 10.5303/PKAS.2005.20.1.125
In this paper, we propose a small-scale Gigabit VLBI observing system for the Korean VLBI Network (KVN) under construction. The system consists of high-speed sampler, IP-VLBI board, PC-VSI board, and software correlator. Radio signal received by receiver is sampled by high-speed sample. at 1 Gsps (Gigabit sample per second) rate with 2 bits quantization. The digitized signal is recorded in PC and the software correlator does the cross correlation. IP-VLBI board will be used for the geodesy VLBI observation, while PC-VSI board is for the astronomical VLBI observation. The PC-VSI board adopts the VSI-H (VLBI Standard Interface Hardware). The proposed system is based on commercial PCs and therefore can be built inexpensively.
ALGORITHM DEVELOPMENT FOR POSITION CORRECTIONS OF FIMS DATA
Lim, Y.M. ; Seon, K.I. ; Min, K. ; Ryu, K.S. ; Park, J.W. ; Kim, I.J. ; Shinn, J.H. ; Lee, D.H. ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 135~141
DOI : 10.5303/PKAS.2005.20.1.135
The FIMS(Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean Science Technology SATellite, STSAT-1, has performed various astronomical observations, including the Cygnus Loop, Vela supernova remnants, LMC(Large Magellanic Cloud), since its launch on September 2003. It has been found that the attitude information provided by spacecraft bus system has the errors of more than about 10-15 arcmins due to the time offset problem and errors in attitude knowledge. We develop an algorithm for correction of position errors in FIMS data. The aspect for the FIMS data is determined by comparing the positions of observed bright stars with the Tycho-II and TD-1 catalogs. The position errors of the bright stars along the scanning (
) and spatial (
) directions were considered as functions of
, ignoring errors in position angle. The corrected positions of the bright stars coincided very well to their Tycho-II and TD-I positions. The correction algorithm is essential for the FIMS data analysis, and is being used for the FIMS data analysis.
OPTO-MECHANICAL DESIGN OF THE KASINICS
Yuk, I.S. ; Lee, S.L. ; Jin, H. ; Seon, K.I. ; Pak, S. ; Lee, D.H. ; Nam, U.W. ; Moon, B.K. ; Cha, S.M. ; Han, J.Y. ; Kyeong, J.M. ; Kim, K.H. ; Yang, J.S. ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 143~149
DOI : 10.5303/PKAS.2005.20.1.143
KASI (Korea Astronomy and Space Science Institute) is developing the near-infrared camera system named KASINICS (KASI Near-Infrared Camera System) which will be installed at the 60cm f/13.5 Ritchey-Chretien telescope of the Sobaeksan Optical Astronomy Observatory (SOAO). The camera system is optimized for JHKL bands and has a 6 arcmin FOV. The optical system consists of two spherical mirrors and a 8-position filter wheel. With the exception for the dewar window, all optical elements are cooled inside cryogenic dewar. Since the Offner system is adopted to prevent thermal noises from outside of the telescope primary mirror, the secondary mirror of the Offner system acts as a cold Lyot stop. The optical performance does not change by temperature variations because the Aluminum mirrors contract and expand homogeneously with its mount. We finished the design and fabrication of the optical parts and are now aligning the optical system. We plan to have a test observation on 2006 January.
GHOST ANALYSIS FOR THE OPTICS SYSTEM OF THE KASINICS
Lee, Sung-Ho ; Yuk, In-Soo ; Jin, Ho ; Pak, Soo-Jong ; Han, Jeong-Yeol ; Lee, Dae-Hee ; Kong, Kyung-Nam ; Cho, Seung-Hyun ; Park, Young-Sik ; Park, Jang-Hyun ; Han, Won-Yong ;
Publications of The Korean Astronomical Society, volume 20, issue 1, 2005, Pages 151~161
DOI : 10.5303/PKAS.2005.20.1.151
The reimaging optics of the KASINICS (KASI Near Infrared Camera System) includes many transparent components like an entrance window, band-pass filters, and blocking filters. As observational targets or in-field background objects, bright stars may cause optical ghosts that can significantly degrade the system performance of the KASINICS. We estimated analytically the relative brightness of ghost components with respect to a point source and examined the effects of tilting optical components as a method of suppressing ghosts. We also performed numerical ray tracings including all the optical components and found the results are consistent with those of the analytic estimations. We conclude that the KASINICS will not suffer from significant ghost effects with appropriate anti-reflection coatings and fittings for the optical components.