본 연구에서는 최근 발표된 가이아 자료를 이용하여 늙은 산개성단 M67의 운동학적 연구 결과를 발표하고자 한다. 사전 연구에서 선정한 934개 별들의 분포로부터 성단의 크기 및 구조를 조사하였다. M67의 투영된 중심거리에 따른 구성원의 표면 밀도 분포를 통해 성단 겉보기 반지름과 구성원의 50%를 포함하는 반지름(half-number radius, rh) 을 각각 약 30′(7.6 pc) 및 12.′4(3.1 pc)으로 결정하였다. 또한 이 분포를 King의 밀도 모형에 맞추어 성단 중심부 반지름(core radius, rc) 4.′0(1.0 pc)을 얻었다. 성단의 색-등급도를 등연령 곡선과 비교하여 나이를 약 4 0억 년으로 추정하였 고, 이는 이전 연구의 결과들과 잘 일치한다. 성단 구성원들의 상대적인 고유운동을 조사한 결과, rh보다 안쪽에 위치한 구성원의 고유운동 방향은 등방하게 나타나는 반면, 외곽에 있는 별들은 성단 중심 방향으로 운동하고 있는 것으로 나 타났다. 이것은 성단의 외곽이 수축하고 있다는 것을 의미한다. rc 이내에 분포하는 별들의 시선속도를 분석한 결과, 천 구 상에서 동-서 방향(위치각 100o-280o)으로 놓여있는 축을 중심으로 성단이 회전 하고 있음을 발견하였다. 이것은 성 단의 형성 이후에도 오랜 시간 동안 성단의 회전이 지속될 수 있음을 의미한다. M67이 비리얼 평형 상태에 있다고 가 정하여 계산한 운동학적 질량은 약 1600 M⊙이다. M67의 동역학적 이완시간은 약 1.9억 년 정도로 예상되며 이것은 성단의 나이인 4 0억 년보다 짧다. 그러므로 이 성단은 동역학적으로 이완된 상태라고 할 수 있다. 실제로 성단 중심으 로부터 거리에 따른 별들이 평균 질량이 작아지는 질량분리 현상을 확인하였다.

본 연구의 목적은 고등학교 지구과학 교육에서 쉽게 다룰 수 있는 소형 망원경과 DSLR 카메라를 활용하여 산개성단을 관측하고, 이를 통해 수집한 데이터를 활용하여 천문학자들과 같은 연구 방법으로 산개성단까지의 거리를 탐구할 수 있는 천체 관측 교육 프로그램을 개발하는 것이다. 2015개정 과학과 교육과정을 분석하여 고등학교 지구과학 교과 교육에 적합한 과학 동아리 활동 수업 자료와 교사용-학생용 학습 콘텐츠를 개발했다. 지구과학 교육과 천문학 분야의 전문가(교사) 6명이 패널로 참가하였고, 패널들 간의 상호간 신뢰도를 구축한 후, 프로그램의 타당도를 검증했다. 총 10차시 수업자료로 개발된 프로그램은 내용타당도(CVI. .89)와 현장 적합성 정도(리커트 5점 척도, 4.17) 검사에서 매우 만족스러운 검증 결과를 받았다. 프로그램에 대한 패널들의 의견 반영과 델파이 분석으로 개발 프로그램을 지속적으로 수정-개선하여 완성하였다. 개발된 프로그램을 고등학교 천체 동아리 학생들(N=9)을 대상으로 시범적 예비수업에 적용한 결과, 학생들의 수업 만족도가 4.48로 매우 높았다. 본 연구의 천체 관측 교육 프로그램을 천체 탐구의 융합교육 활동으로 활용한다면 학생들의 우주와 천체에 대한 관심과 호기심, 탐구 능력 증진에 기여할 수 있을 것이다.

Through the short-period variability survey program, we obtained time-series BV CCD images for 1.5° X 1.0° region around the young open cluster NGC 457. As a result, we have detected 61 variable stars including 31 new ones after checking light curves of all stars by eyes. The 61 variable stars were included 14 δ Scuti variable stars, a β Cephei variable star, 10 variable Be and slowly pulsating B stars, 13 eclipsing binary stars, 21 semi-long periodic or slow irregular variables and an RR Lyrae variable star, respectively. Many variable B-type stars were known through a well-defined zero-age main sequence to the β Cepheid region of NGC 457. Most of the variable B-type stars found this paper were known variable stars. But, 11 out of 14 δ Scuti variable stars were newly discovered. The new variable stars except for δ Scuti stars were 4 variable B-type stars, 5 eclipsing binaries and 11 semi-long periodic or slow irregular variables. We have performed frequency analysis for all δ Scuti stars, a β Cepheid star and an RR Lyrae star.

Through time-series BV CCD photometry of the open cluster NGC 225 region, we have detected 30 variable stars including 22 new ones. They are five δ Scuti-type variable stars, a slowly pulsating B star, six eclipsing binary stars and 18 semi-long periodic or slow irregular variables, respectively. We have performed multiple-frequency analysis to determine pulsation frequencies of the δ Scuti-type stars and a slowly pulsating B star, using the discrete Fourier transform and linear least-square fitting methods. We also have derived the periods and amplitudes of 6 eclipsing binaries and a long-period variable star from the phase tting method, and presented the light curves of all variable stars. A slowly pulsating B star is a member of NGC 225, but δ Scuti-type stars are not members from the positions in the color-magnitude diagram and the radial distancies from the center of the cluster. From Dias et al. (2014, A&A, 564, 79), only three variable stars including the slowly pulsating B star are members of clusters: two are in NGC 225 and one is in Stock 24. But a variable star in Stock 24 is not a member of the cluster because of its position of color-magnitude diagarm.

As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observa- tory, we obtained time-series BV CCD images in the region of the open cluster NGC 1039 (M34). The observations were performed for 22 nights from July 29, 2008 to September 26, 2010. We also made LOAO observations for 10 days from September 18, 2009 to October 30, 2010 to confirm the small variabilties of δ Scuti-type variable stars. In this paper we presented the observational properties of 28 variable stars found in the region. They are seven δ Scuti-type variable stars, two Doradus-type variable stars, four- teen eclipsing binary stars and five semi-long periodic or slow irregular variables, respectively. Only three variables were listed in the GCVS and the rest are newly discovered ones. We have performed multiple- frequency analysis to determine pulsation frequencies of the δ Scuti-type and ɤ Doradus-type variable stars, using the discrete Fourier transform and linear least-square fitting methods. We also have derived the periods and amplitudes of 12 eclipsing binaries from the phase fitting method, and presented the light curves of all variable stars.

This is the second paper on a systematic search for variable stars in Cyg OB3 region. In this paper we present the observational properties of 46 variable stars found in the region. Among them, 27 are eclipsing binaries and others are semi-long periodic or slow irregular variables. Only 5 are known variables and the rest are newly discovered ones. We have obtained the period and amplitude of 20 eclipsing binaries using the phase fitting method, and present the light curves of 46 variable stars.

As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of Cyg OB3 association centered on the open cluster NGC 6871. The observations were performed for 18 nights from September 5, 2008 to September 1, 2009. We found 15 short-period variable stars in the region. They are δ Scuti type stars belonging to the local spiral arm, Orion spur. Among them, only two stars were previously known, and the rest are newly discovered ones. In this paper, we have performed a multiple-frequency analysis to determine frequencies of the 15 δ Scuti type stars, using the discrete Fourier transform and linear least-square fitting methods. One of the newly discovered variable stars is a double-mode δ Scuti type star with the fundamental and the first overtone modes, and two are high amplitude δ Scuti stars.

In the region of the open cluster M48 (NGC 2548), time-series BV CCD images were taken for 22 nights from February 28 in 2008 to March 17 in 2011. From this observation, we found 10 new variable stars. They include five eclipsing binaries, an RR Lyrae, two δ Scuti, and two semi-periodic and/or slow irregular type variable stars. We fail to find the member stars of the open cluster among the 10 variable stars.

In the region of the intermediate open cluster M35 (NGC 2168), the time-series of V CCD images was taken for 12 nights from December 18, 2007 to September 25, 2010. From this observation, we detected 22 variable stars including 15 new ones. They are 6 δ Scuti, a Cepheid, an RR Lyrae, 9 eclipsing binaries and 5 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the δ2 Scuti stars, the multi-frequency analysis was performed using the Discrete Fourier Transform and the linear least-square fitting.

Next to Paper I (Jeon 2009a), time-series BV CCD images of the open cluster M38 were taken for 4 nights on December, 2009. The observations have been carried out for total 27 nights. In addition to the 20 variable stars in the Paper I, the discovery of 44 new variable stars has been presented in this paper: 6δ Scuti stars, 2γ Doradus stars, 18 eclipsing binaries and 18 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the δ Scuti and γ Doradus stars, multi-frequency analysis was performed using the Discrete Fourier Transform and linear least-square fitting. The period search for the eclipsing binaries and the semi-long periodic and/or slow irregular type variable stars was performed by phase fitting method. As a result, the periods for 23 variable stars among the 44 ones were defined.

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, I obtained time-series BV CCD images in the region of the young open cluster M29 (NGC 6913) for 15 nights from May 30, 2008 to September 17, 2009. I observed 48 variable stars including 45 new ones. They consisted of 5 δ Scuti, a Cepheid, 16 eclipsing binaries and 24 semi-long periodic and/or slow irregular type variable stars including β Cephei and LPB type stars. For the rest two ones, the type of variability was not defined. I also checked the variability of the 26 known variable stars listed in the GCVS. Only three ones among 26 known variable stars confirmed variability.

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of an open cluster M38 (NGC 1912) for 23 nights from February 1, 2007 to December 7, 2008. We found 18 δ Scuti stars and 2 γ Doradus stars. Among them, only 3 δ Scuti stars were known ones. From the color-magnitude diagram (CMD) of M38, most of them have been located in the instability strip. The two γ Doradus stars have been located within γ Doradus strip of M38. But, only four δ Scuti stars were located within radius 10' from the center of M38. To confirm of their membership for M38, we need more study, such as, proper motion by spectroscopic observation.