δ Scuti형 변광성 BO Lyn의 파장에 따른 광도곡선 차이를 알아보기 위해서 보현산천문대의 1.8m 반사망원경과 적외선 검출기 KASINICS를 이용한 측광 관측을 수행하였다. 2011년 3월 26일부터 4월 1일까지 총 7일간의 관측 자료 로 J, H, Ks필터 광도곡선을 얻어 기존에 보고된 V필터에서의 광도곡선과 비교하여 주기, 극대점, 진폭, 형태에 대한 차이를 알아보았다. 적외선 광도곡선의 주기 분석 결과 단일 주파수해 f1=10.712 cycle/day, 주기 P=0.09335±0.00002 days의 값을 얻었으며, 파장에 따른 주기의 차이는 나타나지 않았다. 적외선에서는 2f1에 해당하는 주파수가 검출되었는 데, 이는 고진폭 δ Scuti형 변광성의 특징인 비대칭적인 광도곡선의 형태를 잘 설명해준다. 극대점의 위치를 비교한 결 과 계산된 V필터의 예상 극대점보다 관측된 적외선 극대점이 전체 주기의 약 0.3에 해당하는 만큼 더 늦게 나타났다. 진폭은 ΔJ/ΔV=0.328, ΔH/ΔV=0.216, ΔKs/ΔV=0.211로 파장이 길어질수록 변광의 폭이 더 작게 나타났다. 파장에 따른 극대점의 지연과 변광폭의 차이는 맥동변광성의 밝기 변화가 주로 온도변화에 기인하기 때문인 것으로 여겨진다.

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 order to determine color excess in the uvbyβ color system for high amplitude ± Scuti stars, reddening free [m1], [c1], and β indices data were obtained from the existing literature for 21 stars. Then, the three intrinsic relations of (b- y)0 - [m1], (b- y)0 -[c1], and (b-y)0 - β were investigated. Among these, it was shown that the (b-y)0 -[c1] relation is the most useful. By establishing intrinsic (b-y)0-[c1] relations for six reddening calibration stars, color excesses of other stars were determined.

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.

[ δ ] Scuti형 변광성 HR 2707에 대해 한국교원대학교 청람천문대의 40 cm 카세그레인식 반사 망원경과 1K CCD(AP8p)를 사용하여 2001년 11월 13일부터 2002년 2월 20일까지 45일간 시계열 관측을 수행하였다. B, V필터를 이용한 측광 관측으로부터 3,011장의 V필터 영상과 6,562장의 B 필터 영상을 획득하였다. 이들 자료 중 2002년 1월의 7일간 V 필터 관측 자료는 국제공동 관측에 사용되었다(Lopez de Coca et al., 2003). 변광성의 맥동 주파수를 검출하기 위하여 이산 푸리에 변환(DFT)과 선형 최소자승법을 이용하여 8개의 맥동 주파수를 찾았으며, 이전 관측 자료에서 얻어진 주파수와 비교하여 HR 2707의 진짜 맥동 주기는 Lopez de Coca et at.(2003)의 연구에서 얻은 f1, f2, f3, f4, f5의 5개의 주기와 우리의 연구로부터 얻은 f4까지 6개로 결정하였다.

Through time-series CCD photometry using a 130mm refractor of Busan Science Academy, we found a new δ Scuti type variable star, esc 03665-00576. We performed following observations using a 1.8m telescope of Bohyunsan Optical Astronomy Observatory. Three frequencies have been derived by multiple-frequency analysis, which are 10.968, 7.156 and 15.182cycle day−1, respectively. V-amplitude of esc 03665-00576 is ΔV= 0.04.

Through time-series CCD photometry using a 155mm refractor, we found a new δ Scuti type variable star, HD 235428, near a known bright δ Scuti type star, DQ Cep. We performed follow-up observations using a 61cm telescope at Sobaeksan Optical Astronomy Observatory. Four frequencies have been derived by multiple-frequency analysis, which are 15.804, 5.498, 15.351 and 24.516cycle day−1 , respectively. V-amplitude of HD 235428 is ΔV = 0.026.

New uvby photoelectric photometry was carried out for a δ Scuti variable, HR1170. By applying the Fourier method and the linear least square method, three frequencies were derived: f 1 = 10.06134 c / d ( P 1 = 0. d 0994 ). f 2 = 11.91754 c / d ( P 2 = 0. d 0839 ). f 3 = 18.96776 c / d ( P 3 = 0. d 0527 ). From the observed pulsational constants and from the phase difference and amplitude ratios for color(b-y) and magnitude y. three different pulsation modes (n, l) of f 1 ( 0 , 0 ) , f 2 ( 1 , 2 ) , f 3 ( 3 , 2 ) are deduced, indicating the existence of nonradial mode in HR1170. Some physical parameters indicate that HR1170 is evolving at the stage of H-shell burning.

High resolution spectroscopic observation of V1719 Cyg were made at 1.8 meter telescope of Bohyunsan Optical Astronomy observatory in Korea. Spectral resolving power was R=45,000, signal to noise ratio S/N>100. The abundances of 28 chemical elements from carbon to dysprosium were found with the spectrum synthesis method. The abundances of oxygen, titanium, vanadium and elements with Z>30 are overabundant by 0.2–0.9 dex with respect to the solar values. Correlations of derived abundances with condensation temperatures and second ionization potentials of these elements are discussed. The possible influence of accretion from interstellar environment is not so strong as for ρ Pup and other stars with similar temperatures. The signs of accretion are absent. The comparison of chemical composition with solar system r- & s-process abundance patterns shows the enhancement of the photosphere by s-process elements.