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VARIABLE STARS IN THE REGION OF CYG OB3 ASSOCIATION CENTERED ON THE OPEN CLUSTER NGC 6871 I: δ SCUTI TYPE STARS

산개성단 NGC 6871을 중심으로 한 Cyg OB3 성협 영역의 변광성 I: δ Scuti 형 변광성

  • Received : 2012.10.09
  • Accepted : 2012.11.02
  • Published : 2012.12.31
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Abstract

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 ${\delta}$ 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 ${\delta}$ 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 ${\delta}$ Scuti type star with the fundamental and the first overtone modes, and two are high amplitude ${\delta}$ Scuti stars.

NGC 6871을 중심으로 시계열 관측한 Cyg OB3 성협영역에서 모두 15개의 단주기 변광성을 찾았다. 이들은 모두 국부나선팔에 속한 ${\delta}$ Scuti 형 변광성으로 보인다. 그림 5의 영연령주계열 상에서 밝은쪽에 속한 V1-V4는 분광형이 모두 A, F 형으로서 Cyg OB3 성협보다 먼 거리에 있는 ${\beta}$ Cephei 형 변광성이라기 보다는 국부나선팔의 앞쪽에 놓인 ${\delta}$ Scuti 형 변광성이었다. 15개의 ${\delta}$ Scuti 형 변광성 중에는 2개(V1과 V3)는 GCVS에 ${\delta}$ Scuti 형 변광성으로 분류되어 이미 알려진 변광성이고, 나머지는 모두 새로 발견한 것이다. 새로 발견한 변광성 중에는 한 개의 이중모드 ${\delta}$ Scuti 형 변광성(V3)과 2개의 HADS 변광성(V13과 V14)이 포함되었다. 시계열 관측과는 별도로 표준화 관측을 수행하여 관측 영역의 색-등급도를 얻었는데 그림 6에서 Massey etal.(1995)의 결과와 잘 맞았다.

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References

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  1. VARIABLE STARS IN THE REGION OF CYG OB3 ASSOCIATION CENTERED ON THE OPEN CLUSTER NGC 6871 II vol.28, pp.3, 2013, https://doi.org/10.5303/PKAS.2013.28.3.083