http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Toward early scientific results on AGNs: 'KAVA'(KVN and VERA array) joint AGN WG report
손봉원,이상성,Sohn, Bong Won,Kino, Motoki,Niinuma, Kotaro,Lee, Sang-Sung,Honma, Mareki,Nagai, Hiroshi,Sascha, Sascha Trippe,Jung, Taehyun 한국천문학회 2012 天文學會報 Vol.37 No.2
We report the results of KVN-VERA('KAVA'; KVN and VERA Arrary) AGN WG test observation in 2011 and 2012. The results from these commisioning years show that 'KAVA' is able to produce noble images of radio loud AGNs at 22 and 43GHz. This dedicated high frequency VLBI facility will be especially competitive for the regions where conventional low freuquency facilities see the optically thick part of synchrotron radiation. In the second part of this talk, we report the early science activities of the AGN WG. Sgr A*, Jet acceleration zone of M87, extremely young radio galaxies are the prime cadidates of the joint activities. Lastly we will stress how the phase-referencing 'KAVA' does enhance the imaging sensitivity and open new era of VLBI AGN researches.
Early Science of KVN: 43GHz fringe survey
이상성,김종수,정태현,손봉원,변도영,Lee, Sang-Sung,Petrov, Leonid,Kim, Jongsoo,Jung, Taehyun,Sohn, Bong Won,Byun, Do-Young 한국천문학회 2012 天文學會報 Vol.37 No.2
This paper presents the results of one of early sciences with Korean VLBI Network (KVN): a large fringe survey of compact radio sources at 43GHz. We established the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 623 sources have not been observed before at Q-band with VLBI. The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22--129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to $-40{\circ}$. Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in a range of 115--180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with the median formal uncertainty 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies 22 GHz and higher at 3/4 of the celestial sphere.
Monitoring of gamma-ray bright AGN BLLAC and OJ287 with KVN 21m radio telescopes
한명희,이상성,변도영,양지혜,백준현,손봉원,Han, Myoung-Hee,Lee, Sang-Sung,Byun, Do-Young,Yang, Jee-Hye,Baek, Jun-Hyun,Sohn, Bong-Won 한국천문학회 2012 天文學會報 Vol.37 No.2
MOGABA is a project monitoring of gamma-ray bright AGN(Active Galactic Nuclei). Since May 2011, we have observed total flux, degree of linear polarization, and polarization angle of about twenty AGN once a week at 22, 43 and 86GHz using KVN(Korean VLBI Network) 21m radio telescopes. We have observed variation of total flux of BLLAC and OJ287 from May 2011 to March 2012. We have observed flares of total flux at 22GHz for those sources from October 2011 to November 2011. In this paper we report the variation of total flux, degree of linear polarization and polarization angle at 22, 43, 86GHz for BLLAC and OJ287.
백준현,이상성,변도영,양지혜,한명희,손봉원,Baek, Jun-Hyun,Lee, Sang-Sung,Byun, Do-Young,Yang, Jee-Hye,Han, Myoung-Hee,Sohn, Bong-Won 한국천문학회 2012 天文學會報 Vol.37 No.2
AGN(Active Galactic Nucleus) consists of a supermassive black hole located at its center, an accretion disk around the black hole, and bipolar jets. Since May 2011, we have performed the MOGABA(Monitoring Of GAmma-ray Bright AGN) project for observing gamma-ray bright AGN once a week at multifrequencies using KVN(Korean VLBI Network) 21m radio telescopes. The MOGABA project is the observations for measuring the degree of polarization, polarization angle, and total flux of about 20 AGN at 22, 43 and 86GHz. By this project, we are able to investigate polarization characteristics, spectral index, and variation of rotation measure at radio wavelengths of gamma-ray bright AGN and to study possible relation between gamma-ray flares and magnetic field structure change in AGN. According to previous research, gamma-ray flares of some AGN are coincident with large changes in angle of linear polarization. In this paper we report the preliminary results of linear polarization and total flux at 22, 43, 86GHz of gamma-ray bright quasars 3C279 and 1510-089 showing noticeable variation of total flux at 22GHz in late 2011, and discuss possible correlation with gamma ray light curves.
MOGABA: Monitoring of Gamma-ray Bright AGN with KVN 21-m radio telescopes at 22, 43 and 86GHz
이상성,변도영,백준현,한명희,양지혜,손봉원,Lee, Sang-Sung,Byun, Do-Young,Baek, Junhyu,Han, Myounghee,Yang, Jihae,Sohn, Bong Won 한국천문학회 2012 天文學會報 Vol.37 No.2
We report preliminary results of MOGABA project for monitoring total flux density, linearly polarized flux, and polarization angle at 22, 43 and 86GHz of Gamma-ray bright AGN (Active Galactic Nuclei) with KVN (Korean VLBI Network) 21-m radio telescopes. The project has been conducted in one year since May 2011 with an effective monitoring cycle of 1 week, observing four main objects (3C 454.3, BL Lac, 3C 273, and 3C 279). More objects were included in the source list when they had flared in Gamma-ray. Especially, we included a compact radio source at the Galactic center, SgrA* since Jan. 2012. In this paper, we report the current status of the project and preliminary results for the monitoring observations.
제도흥,이원규,김수연,정문희,송민규,정태현,변도영,김승래,손봉원,위석오,한석태,강용우,Je, Do-Heung,Lee, Won-Kyu,Kim, Soo-Yeon,Chung, Moon-Hee,Song, Min-Kyu,Jung, Taehyun,Byun, Do-Young,Kim, Seung-Rae,Sohn, Bong-Won,Wi, Seog-Oh,Han, Seog-T 한국천문학회 2013 天文學論叢 Vol.28 No.3
A fiber-optic reference signal transmission system, which transmits the 1.4 GHz reference signal from H-maser to receiver cabin in radio telescopes, was adopted for compensating the phase changes due to temperature variation and antenna movement. At the first experiment, the remote signal's phase changed more than 15 degrees at 1.4 GHz. We found unstable components in sub-system experiments and replaced them. The main cause of unstable phase stability was the unaligned polarization axis between Laser Diode and Mach-Zehnder Modulator (MZM). The improved system stability showed $1{\times}10^{-16}$ allan standard deviation at 1,000 sec integration time with the antenna fixed. When the antenna moves in the azimuth axis, the 1.4 GHz remote signal showed the phase change smaller than 0.2 degrees.
대용량 VLBI 데이터 전송을 위한 네트워크 설계 및 시스템 관리
송민규 ( Min Gyu Song ),김현구 ( Hyun Goo Kim ),손봉원 ( Bong Won Sohn ),변도영 ( Do Young Byun ),오세진 ( Se Jin Oh ),노덕규 ( Duk Gyoo Roh ),위석오 ( Seog Oh Wi ),강용우 ( Yong Woo Kang ),이상성 ( Sang Sung Lee ),오충식 ( Chung 대한설비관리학회 2010 대한설비관리학회지 Vol.15 No.4
In this paper, we discuss the network design and construction, which is correspond to the basis for the implementation of e-VLBI. Because the data acquired from VLBI observation is high speed of Gbps, it is hard to satisfy astronomers`s demand of high speed data transfer by the use of general network. It is necessary to upgrade of all over the network from backbone to metro or local area, and proper network systems should be installed. For this reason, we designate KREONET(Korea REsearch Open NETwork) administered by the KISTI as e-KVN(Korean VLBI Network)`s backone network, and KT`s MSPP(Multi Service Provisioning Platform) was used as metro network. We install optical device modules and network switch as well as organize network of VLBI systems. It allows KVN to have a network architecture that could transfer observed VLBI data at Gbps speed. Also, we apply VLAN(Virtual LAN) configuration to e-KVN for the network integration and efficient management