• 천문학회보
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• 제36권2호
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• pp.118-118
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• 2011

We executed a simultaneous survey of 22 GHz water maser and 44 GHz methanol maser toward 290 shocked $H_2$ emitting regions, which were identified from the galactic plane survey at $H_2$ 2.122 micrometer (UKIRT Widefield Infrared Survey for $H_2$; UWISH2). The primary goal of this observation is to characterize the H2 emission sources whether they are sincerely due to the outflows of young stellar objects or other shocked emission from older/evolved objects. We discovered 15 water maser sources and 15 methanol maser sources which provide the detection rate of around 5 percents. Most of detected sources have IRAS sources, infrared dark clouds, and/or submilimeter sources in the beam size of KVN single dish. In this poster, we will present the detailed results of our survey observation and discuss about the star formation rate in the galactic plane.

• 천문학회보
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• 제36권2호
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• pp.127.1-127.1
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• 2011

Over the past several years the millimeter wave VLBI(Veryl Long Baseline Interferometry) observations have been intensively carried out. However In millimeter and sub-millimeter waves observations for VLBI, it is crucial to calibrate correctly the phase variations of the electromagnetic waves propagation through the troposphere. To do this, KVN(Korean VLBI Network) has a unique multi-frequency bands receiver system which is able to perform the simultaneous observations in up to four bands such as 22, 43, 86, and 129GHz. The phase of a source at 22GHz can be used to calibrate the phase of the same source at higher frequency bands. The phase calibration using multi-frequency bands receiver system is possible because the phase fluctuations from a given amount of waver vapor increase linearly with frequency. That is to say that troposphere is non-dispersive property in terms of tropospheric delay fluctuations. In this talk, We present results of test observation for multi-frequency bands receiver system.

• 천문학회보
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• 제36권2호
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• pp.60.1-60.1
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• 2011

We present the preliminary results of the pilot observations for the fringe survey at 43 GHz with the VLBI Exploration of Radio Astrometry (VERA). The main goals of the fringe survey are to establish a full list of phase calibrators for the VERA dual-beam astrometric observations, and for the KVN multi-frequency phase referencing observations. We performed two 24 hours experiments as a pilot observation to test the feasibility of the fringe survey. Each source from a list of 220 sources has been observed in one scan for 2 minutes. 67 sources were detected with the SNR threshold of 3.5. The correlated flux densities of the detected sources are presented in four ranges of projected baseline lengths.

• 천문학회보
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• 제38권1호
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• pp.44.2-44.2
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• 2013

We probe the feasibility of high-frequency radio observations of very rapid flux variations in compact active galactic nuclei (AGN). Our study assumes observations at 230 GHz with a small 6-meter class observatory, using the SNU Radio Astronomical Observatory (SRAO) as example. We find that 33 radio-bright sources are observable with signal-to-noise ratios larger than ten. We derive statistical detection limits via exhaustive Monte Carlo simulations assuming (a) periodic, and (b) episodic flaring flux variations on time-scales as small as tens of minutes. We conclude that a wide range of flux variations is observable. This makes high-frequency radio observations - even with small observatories - a powerful probe of AGN intra-day variability; especially, those observations complement observations at lower radio frequencies with larger observatories like the Korean VLBI Network (KVN).

• 천문학회보
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• 제34권1호
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• pp.116.1-116.1
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• 2009

• 천문학회보
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• 제34권1호
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• pp.115.2-115.2
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• 2009

• 천문학회보
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• 제37권2호
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• pp.94.2-94.2
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• 2012

NASA는 지난 15년간 주요 과학미션 비용의 약 1%를 교육과 public outreach에 투자했으며 NSF 천문학분야 연구비의 약 6% 이상이 교육과 특별활동에 사용되고 있다는 보고가 있다. 국내 천문학 연구 프로젝트에서도 교육 및 public outreach에 대한 예산 할당과 프로젝트의 교육적 활용 및 대국민 홍보 활동을 위한 구체적인 연구가 필요한 상황이다. 이번 연구에서는 국내 천문학 연구 프로젝트의 교육적 활용을 위하여 1)NASA의 과학미션과 관련된 교육자 가이드들을 사례조사 하였고, 2)사례조사 결과와 2007 개정 과학과 교육과정을 고려하여 KMTNet 프로젝트의 교육자 가이드를 e-book 형태로 개발 하였다. 이번 발표에서는 개발된 교육자 가이드의 배포 및 활용 방안과 국내에서 수행중인 천문학 프로젝트(KVN, GMT, SKA, ALMA 등)들의 교육자 가이드 제작을 위한 사업방안을 소개하고 산업체, 학교, 연구기관에 종사하는 분야별 전문가들로 부터 다양한 의견을 청취하고자 한다.

• 천문학회보
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• 제36권1호
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• pp.50.1-50.1
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• 2011

We report the results of the monitoring of a flaring gamma-ray blazar, 3C454.3 in total flux density at 22 and 43GHz and in polarization at 22GHz with KVN Ulsan 21-m radio telescope every 3-4 days from 19 November 2010 to 31 January 2011. After an extraordinary 5-day gamma-ray outburst in November 2010, the radio total flux density at 22/43GHz and the linear polarization at 22GHz has been decreased with a variation of a short time scale. In this paper, we also discuss a spectral change of 3C454.3 at 22 and 43GHz after the extraordinary gamma-ray outburst.

• 천문학회보
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• 제36권1호
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• pp.72.1-72.1
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• 2011

한국우주전파관측망(Korean VLBI Network, KVN)을 이루는 21m 전파망원경 수신기들의 전파세기를 모니터링하기 위하여, 전파세기 측정기를 설계, 제작 중에 있다. 이 장치는 수신된 우주전파신호를 주파수로 변환해서, 전파관측 중의 모니터링이나 수신신호특성을 파악하는데 필요한 장치이다. 지난 연구(강용우 외, 2010)에서 이러한 회로 특성 파악과 개선을 위하여, 다양한 실험을 할 수 있게 전파세기 시험용 측정기를 제작하고 시험한 바 있다. 본 연구에서는 시험용 측정기의 시험 결과를 바탕으로, EPLD(Erasable Programmable Logic Devices)를 이용한 전파세기측정기를 새로 개발 중에 있다. 이에 지금까지의 개발 내용을 소개하고자 한다.

• 천문학논총
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• 제38권2호
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• pp.75-89
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• 2023

Technosignature, previously known as SETI(search for extraterrestrial intelligence), is the scientific evidence of past or present extraterrestrial civilizations. Since NRAO's Project Ozma was performed in 1960, most of the noticeable technosignature searches have been done by radio telescopes, hoping to find strong and narrow bandwidth signals that cannot be explained by known natural processes. Recently, the Breakthrough Listen project has opened a new opportunity for technosignature by utilizing both optical telescopes, radio telescopes, and next-generation radio telescope arrays. In this review, mainly based on NASA Technosignatures Workshop (2018), we review the current trends of technosignature surveys, as well as other possible methods for detecting technosignature. Also, we suggest what the Korean community could contribute the technosignature research, including the new SETI project with Korea VLBI Network (KVN).