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      • SCIESCOPUSKCI등재

        CCD PHOTOMETRY OF STANDARD STARS AT MAIDANAK ASTRONOMICAL OBSERVATORY IN UZBEKSTAN: TRANSFORMATIONS AND COMPARISONS

        Lim, Beomdu,Sung, Hwan-Kyung,Bessell, M.S.,Karimov, R.,Ibrahimov, M. The Korean Astronomical Society 2009 Journal of The Korean Astronomical Society Vol.42 No.6

        Observation of standard stars is of crucial importance in stellar photometry. We have studied the standard transformation relations of the UBV RI CCD photometric system at the Maidanak Astronomical Observatory in Uzbekistan. All observations were made with the AZT-22 1.5m telescope, SITe 2k CCD or Fairchild 486 CCD, and standard Bessell UBV RI filters from 2003 August to 2007 September. We observed many standard stars around the celestial equator observed by SAAO astronomers. The atmospheric extinction coefficients, photometric zero points, and time variation of photometric zero points of each night were determined. Secondary extinction coefficients and photometric zero points were very stable, while primary extinction coefficients showed a distinct seasonal variation. We also determined the transformation coefficients for each filter. For B, V, R, and I filters, the transformation to the SAAO standard system could be achieved with a straight line or a combination of two straight lines. However, in the case of the U filter and Fairchild 486 CCD combination, a significant non-linear correction term - related to the size of Balmer jump or the strength of the Balmer lines - of up to 0:08 mags was required. We found that our data matched well the SAAO photometry in V, B - V, V - I, and R - I. But in U - B, the difference in zero point was about 3.6 mmag and the scatter was about 0.02 mag. We attribute the relatively large scatter in U -B to the larger error in U of the SAAO photometry. We confirm the mostly small differences between the SAAO standard UBV RI system and the Landolt standard system. We also attempted to interpret the seasonal variation of the atmospheric extinction coefficients in the context of scattering sources in the earth's atmosphere.

      • SCIESCOPUSKCI등재

        AN EAST-ASIAN EXTRA-SOLAR PLANET SEARCH NETWORK

        IZUMIURA HIDEYUKI The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2

        We are undertaking an extra-solar planet search around G-type giant stars by means of Doppler technique using an iodine absorption cell installed to the high dispersion echelle spectrograph for the 188 cm reflector at Okayama Astrophysical Observatory (Okayama Planet Search Program, OPSP). Having detected the first planet candidate (Sato et al. 2003)the search has been proved very promising. Taking advantage of this success, we are trying to develop OPSP to an international collaborative work. We here report the current status of our efforts for establishing such collaborations, namely, those with Chinese and Korean astronomers. We also propose to establish an East-Asian network to search for extra-solar planets around G-type giant stars with the transit detecting technique as well as the Doppler technique, asking other persons/groups to join us to enjoy the planet search.

      • KCI등재

        LATEST RESULTS OF THE MAXI MISSION

        MIHARA, TATEHIRO The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

        Monitor of All-sky X-ray Image (MAXI) is a Japanese X-ray all-sky surveyer mounted on the International Space Station (ISS). It has been scanning the whole sky since 2009 during every 92-minute ISS rotation. X-ray transients are quickly found by the real-time nova-search program. As a result, MAXI has issued 133 Astronomer's Telegrams and 44 Gamma-ray burst Coordinated Networks so far. MAXI has discovered six new black holes (BH) in 4.5 years. Long-term behaviors of the MAXI BHs can be classified into two types by their outbursts; a fast-rise exponential-decay type and a fast-rise flat-top one. The slit camera is suitable for accumulating data over a long time. MAXI issued a 37-month catalog containing 500 sources above a ~0.6 mCrab detection limit at 4-10 keV in the region ${\mid}{b}{\mid}$ > $10^{\circ}$. The SSC instrument utilizing an X-ray CCD has detected diffuse soft X-rays extending over a large solid angle, such as the Cygnus super bubble. MAXI/SSC has also detcted a Ne emission line from the rapid soft X-ray nova MAXI J0158-744. The overall shapes of outbursts in Be X-ray binaries (BeXRB) are precisely observed with MAXI/GSC. BeXRB have two kinds of outbursts, a normal outburst and a giant one. The peak dates of the subsequent giant outbursts of A0535+26 repeated with a different period than the orbital one. The Be stellar disk is considered to either have a precession motion or a distorted shape. The long-term behaviors of low-mass X-ray binaries (LMXB) containing weakly magnetized neutron stars are investigated. Transient LMXBs (Aql X-1 and 4U 1608-52) repeated outbursts every 200-1000 days, which is understood by the limit-cycle of hydrogen ionization states in the outer accretion disk. A third state (very dim state) in Aql X-1 and 4U 1608-52 was interpreted as the propeller effect in the unified picture of LMXB. Cir X-1 is a peculiar source in the sense that its long-term behavior is not like typical LMXBs. The luminosity sometimes decreases suddenly at periastron. It might be explained by the stripping of the outer accretion disk by a clumpy stellar wind. MAXI observed 64 large flares from 22 active stars (RS CVns, dMe stars, Argol types, young stellar objects) over 4 years. The total energies are $10^{34}-10^{36}$ erg $s^{-1}$. Since MAXI can measure the spectrum (temperature and emission measure), we can estimate the size of the plasma and the magnetic fields. The size sometimes exceeds the size of the star. The magnetic field is in the range of 10-100 gauss, which is a typical value for solar flares.

      • KCI등재

        AMATURE ASTRONOMY AND ASTRONOMY EDUCATION IN INDIA

        CHATTERJEE, SOMENATH The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

        In India, astronomy has been studied from the beginning of civilization. The word amateur means involvement in work for pleasure rather than as a profesion. So, amateur astronomers, in many places, prefer to be called non-professional astronomers. In India, the history of amateur astronomy is quite bright. From the Puranic age astronomy was studied for peoples' daily life. In Ramayana, Mahabharata, there is a lot of evidence of astronomical knowledge. Veda is the main source for studying the history of Indian astronomy. Today astronomy education, consciousness of astronomy education, sky observation, etc. are dependent on non-professional astronomers. Vigyan Prasar, an Indian Govt. organization, is trying to popularize astronomy throughout the country.

      • KCI등재

        RADIO ASTRONOMY AT WRC-03

        Chung, Hyun-Soo,Ahn, Do-Seob,Park, Jong-Min,Oh, Dae-Sub,Kim, Hyo-Ryoung,Rho, Duk-Gyoo,Je, Do-Heung The Korean Astronomical Society 2003 天文學論叢 Vol.18 No.1

        Most radio astronomy issues at WRC-03 (World Radiocommunication Conference-03) revolved around satellite downlink allocations, particularly to NGSO (Non-Geostationary Satellite Orbit) satellite systems, in bands adjacent to or close to a radio astronomy frequency band. Out of a total of 50 agenda items, ten were of interest to radio astronomers. This paper provides some details about the important outcome of the radio astronomy related issues at the WRC-03.

      • KCI등재

        AN ACCOUNT OF INDIAN ASTRONOMICAL HERITAGE FROM THE 5th CE to 12th CE

        CHATTERJEE, SOMENATH The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

        Astronomical observation is the beginning of scientific attitudes in the history of mankind. According to Indian tradition, there existed 18 early astronomical texts (siddhantas) composed by Surya, Pitamaha and many others. Varahamihira compiled five astronomical texts in a book named panchasiddhantika, which is now the link between early and later siddhantas. Indian scholars had no practice of writing their own names in their works, so, it is very difficult to identify them. Aryabhata is the first name noticed, in the book Aryabhatiya. After this point most astronomers and astro-writers wrote their names in their works. In this paper I have tried to analyze the works of astronomers like Aryabhata, Varahamihira, Brahmagupta, Bhaskara I, Vateswara, Sripati and Bhaskaracharya in a modern context and to obtain an account of Indian astronomical knowledge. Aryabhata is the first Indian astronomer who stated that the rising and setting of the Sun, the Moon and other heavenly bodies was due to the relative motion of the Earth caused by the rotation of the Earth about its own axis. He also estabished the 'yuga' theory (one Mahayuga = 432000 years). Varahamihira compiled panchasiddhantika and wrote Brihatsamhita. Brahmagupta is the most distinguished astronomer known to us. His two major works are i) Brahmasphutasiddhanta and ii) Khandkhadaka. Bhaskara I was the follower of Aryabhata. His three known works are Mahabhaskariya, Laghubhaskariya and Aryabhatiyabhasya. Vateswara follows Aryapaksha and Saurapaksha. His master work is Vateswarasiddhanta. Sripati, in his siddhantasekhara, gives the rules for determining the Moon's second inequality. Bhaskara II wrote the most comprehensive astronomical work in Indian astronomy. The result of these works is the account of the Indian astronomical heritage. These works are written in the Sanskrit language. A very few of these manuscripts have been translated in English but many are yet to be done. So, it is necessary to translate these astronomical texts into English with proper commentary for modern scholars. This paper will be helpful in this work.

      • KCI등재

        THE CREATIVE APPROACH FOR DISSEMINATING ASTRONOMY TO THE GENERAL PUBLIC

        PRAMUDYA, Y.,SAWITAR, W. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

        Astronomical outreach activities for the general public who are unfamiliar to astronomy is a challenging task. It requires creative thinking to solve the problem. The amateur astronomical clubs in a number of cities in Indonesia routinely schedule observations at public parks. The interaction between these clubs and formal education institutions is established by face to face interaction and assisted by social media. The physics teachers who took astronomy courses in university are potential resources to enlarge the outreach scope by creating astronomical clubs as an extracurricular activity. Recent progressive trends in astronomy dissemination for the disabled are also a great opportunity to assist the disabled in experiencing hands-on activities based on formal and informal education.

      • SCIESCOPUSKCI등재

        CHARACTERISTICS AND PERFORMANCE OF A FAST CCD CAMERA: DALSTA IM30P

        SEO YOUNG-MIN,PARK KI-WOONG,CHAE JONGCRUL The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.4

        We have been developing a solar observing system based on a fast CCD camera 1M30P made by the DALSA company. Here we examine and present the characteristics and performance of the camera. For this we have analyzed a number of images of a flat wall illuminated by a constant light source. As a result we found that in the default operating mode 1) the mean bias level is 49 ADU/pix, 2) the mean dark current is about 8 ADU /s/pix, 3) the readout noise is 1.3 ADU, and 4) the gain is about 42 electrons/ ADU. The CCD detector is found to have a linearity with a deviation smaller than $6\%$, and a uniform sensitivity better than $1\%$. These parameters will be used as basic inputs in the analysis of data to be taken by the camera.

      • SCIESCOPUSKCI등재

        ON ASTRONOMICAL RECORDS OF DANGUN CHOSUN PERIOD

        LA DAILE,PARK CHANGBOM The Korean Astronomical Society 1993 Journal of The Korean Astronomical Society Vol.26 No.2

        Events of eclipses as well as other major astronomical events observable in the eastern sector of Asian continent are computed and checked with astronomical records of antiquity. Particular attention was given to two types of the events recorded in remaining records of Dangun Chosun Period (DCP): (1) concentration of major planets near the constellation of Nu-Sung $(\beta\;Aries)$ and (2) a large ebb-tide. We find them most likely to have occurred in real time. i.e., when the positions of the sun, moon, and planets happen to be aligned in the most appropriate position. For solar eclipses data, however, we find among 10 solar eclipse events recorded, only 6 of them are correct up to months, implying its statistical significance is no less insignificant. We therefore conclude that the remaining history books of DCP indeed contains important astronomical records, thereby the real antiquity of the records of DCP cannot be disproved.

      • SCIESCOPUSKCI등재

        DESIGN AND MANUFACTURING OF THE CASSEGRAIN INTERFACE MODULE OF THE BOAO ECHELLE SPECTROGRAPH

        KIM KANG-MIN,JANG BE-HO,HAN INWOO,JANG JEONG GYUN,SUNG HYUN CHUL,CHUN MOO-YOUNG,HYUNG SIEK,YOON TAE-SEOG,VOGT STEVEN S. The Korean Astronomical Society 2002 Journal of The Korean Astronomical Society Vol.35 No.4

        Cassegrain interface module (CIM) of the fiber-fed high resolution echelle spectrograph has been designed and manufactured for the 1.8 m reflector at the Bohynsan Optical Astronomy Observatory. We also constructed a long slit spectrograph attached to this CIM, which would replace the earlier rather inefficient medium dispersion spectrometer. We present detailed description for design and manufacturing concepts of the CIM which consists of a slit assembly, slit monitoring system, calibration lamp system and a long slit spectrograph, in order to provide how the overall system and each part. are constructed. The preliminary performance test carried out so far seems to indicate a successful result.

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