• Journal of The Korean Astronomical Society
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• v.42 no.6
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• pp.155-159
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• 2009

In order to determine color excess in the $uvby\beta$ color system for high amplitude $\delta$ Scuti stars, reddening free $[m_1]$, $[c_1]$, and $\beta$ indices data were obtained from the existing literature for 21 stars. Then, the three intrinsic relations of $(b-y)_0$ - $[m_1]$, $(b-y)_0$ - $[c_1]$, and $(b-y)_0$ - $\beta$ were investigated. Among these, it was shown that the $(b-y)_0$-$[c_1]$ relation is the most useful. By establishing intrinsic $(b-y)_0$-$[c_1]$ relations for six reddening calibration stars, color excesses of other stars were determined.

• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.141-149
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• 2007

Preliminary time-series observations for short-period variability survey (SPVS) were carried out using a 155mm refractor and a $2k{\times}3k$ CCD camera at Bohyunsan Optical Astronomy Observatory. We found 21 new variable stars in the $90'{\times}60'$ test field region : 9 eclipsing binary stars, $5{\delta}$ Scuti type stars, a ${\gamma}$ Doradus type star, and 6 long period variables. The observing field center is R.A. $05^h\;00^m\;00^s$, DEC. $50^{\circ}\;00'\;00"$ (J2000.0). The period and amplitude ranges for the short-period variables, i.e., ${\delta}$ Scuti stars, were 0.052day - 0.107day and 0.012mag - 0.064mag, respectively.

• Journal of the Korean earth science society
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• v.37 no.7
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• pp.389-397
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• 2016

In order to investigate the light curve difference in visual and infrared wavelength of ${\delta}$ Scuti variable Bo Lyn, observations were performed using BOAO 1.8m reflecting telescope and an infrared detector, KASINICS, with J, H, and Ks filters. Infrared light curves of total 7 nights were obtained between March and April in 2011, and those were compared to the V-filter light curve to examine the differences in period, time of maximum light, amplitude, and shape. From the periodic analysis of infrared light curve, a single frequency of $f_1=10.712cycle/day$, $P=0.09335{\pm}0.00002days$ was obtained, and there was no difference in the period along different wavelengths. In the infrared light curve, a frequency of $2f_1$ was detected. This frequency well explains the asymmetric shape of light curve, one of the characteristics of high-amplitude ${\delta}$ Scuti variables. We compared the locations of the measured infrared maxima and the predicted maxima of V-filter, finding that the times of maxima were delayed about 0.3 phase at infrared wavelengths. Amplitude ratios were adopted to be ${\Delta}J/{\Delta}V=0.328$, ${\Delta}H/{\Delta}V=0.216$, and ${\Delta}Ks/{\Delta}V=0.211$, with the range of variation being smaller at longer wavelengths. It seems that the differences in the times of maxima and amplitude occurred because the changes in brightness of a pulsating variable star are mainly caused by the change in temperature.

• Publications of The Korean Astronomical Society
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• v.27 no.5
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• pp.399-409
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• 2012

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.