• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.157-170
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• 2009

BVR observations for 52 standard stars were performed using the 1-m reflecter with 2K CCD System of Chungbuk National University Observatory (CBNUO) in 2008. We obtained 1,322 CCD images to establish a correlation between our bvr system and the standard Johnson-Cousins BVR system. We derived the tentative equations of transformation between then as follows; V = v-0.0303(B - V) + 0.0466 B - V = 1.3475(b - v) - 0.0251 V - R = 1.0641(v - r) - 0.0125 Using these equations the magnitudes in V, B-V, and V-R for 197 stars were obtained.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.81-88
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• 2010

A total of 583 observations (193 in ${\Delta}b$, 190 in ${\Delta}v$, 200 in ${\Delta}r$) for V523 Cas was made on 9 nights from September to December in 2008 using the 100 cm telescope with 2K CCD camera of the Chungbuk National University Observatory. With our data BVR light curves were constructed and 9 times of minimum light were determined. We also obtained physical parameters of the V523 Cas system by analysis of the BVR light curves using the Wilson-Devinney code.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.32.1-32.1
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• 2010

The BVR CCD observations of the solar-type contact binary GW Cephei, known as very active dynamically and photometrically, has been made for 20 nights from Nov. 03, 2008 to Dec. 31, 2008 with 1-m reflector of Jincheon station of Chungbuk National University Observatory. A total of 2035 measurements (B: 647, V: 722, R: 666) were obtained to secure new multi-color light curves. From our observations fifteen times of minimum light were newly determined. In this paper both a new period study and an intensive light synthesis were made. Our results will be compared and discussed with the latest thorough studies of the system by Lee et al. (2010).

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.141.1-141.1
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• 2011

New CCD BVR light curves of BD And are presented. Our light curves with nearly equal depths for both primary and secondary eclipses show well-defined photometric waves outside eclipse for all of BVR bandpasses. The orbital period is greatly revised as $0.^d92580519$ which is twice longer than that known previously. Sixteen timings from our observations and thirteen ones from the SuperWASP measurements were calculated. All available timings over 76 years, including ours, were analyzed to figure out the dynamical behavior of the system. It was found that the recent CCD O-C residuals varied in a cyclical way with a period of $9.^y18$ and a semi-amplitude of $0.^d0046$. The secondary period of $9.^y18$ is the most shortest one among those which have been ever found in the short period RS CVn binary stars. The periodic variation most likely arises from the light-travel time effect due to a low-mass ($m_3{\sim}0.88\;M_{\odot}$) tertiary companion moving in an orbit with an large eccentricity ($e_3$=0.70) and a low inclination ($i_3{\sim}28^{\circ}$). The Applegate mechanism could not operate properly in both components because the model parameters require too much large luminosity changes of ${\Delta}L/L_{p,s}$ > 10. The new light curves were synthesized using the 2003 version of Wilson-Divinney code. It was found useful to model two huge spots on the surface of the hotter star and a third-light in order to minimize the residuals from the observations. Astronomical basic parameters were deduced from our photometric solution.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.209-216
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• 1999

Light curves of two near-contact binaries DO Cas and SW Lyn are analyzed to investigate their Roche configurations. We made new BVR observations for DO Cas and employed the published observation data for SW Lyn. Our four night observations for DO Cas were secured over 8 days so that the contamination by the intrinsic light variation is minimized. Based on the WD model, we found that DO Cas could be classified as a near-contact binary, while SW Lyn is better described by semi-detached configuration. Furthermore it is also possible to classify DO Cas as a contact binary. It appears that there are ambiguities in the class of near-contact configuration, and further observations and re-analysis are required to establish the near-contact nature of binary systems.

• Journal of Astronomy and Space Sciences
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• v.20 no.2
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• pp.123-132
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• 2003

We performed CCD photometric observations of the W-type contact binary AB And for 10 nights from November 1995 to December 1999 using the 61-cm reflector and BVR filters at Sobaeksan Optical Astronomy Observatory. From our observations, the seasonal light curves of AB And for 1995, 1996 and 1999 were completed and 8 new times of minimum light were determined. Newly obtained light curves show that strong light variations occurred in AB And during the past five years. We adopted the 1996 light curves as reference ones and obtained the photometric solutions of them with contact mode in the Wilson-Devinney binary code. Assuming such light variations were produced by the existence of a star spot (or star spots) in the analysis, we derived the system parameters and analyzed the 1995 and 1999 light curves by adjusting only the spot parameters. As the results, we interpreted that those light variations are produced by the simultaneous existence of a hot spot and a cool spot on the secondary. We could infer that the hot spot on the secondary is produced due to mass exchange between the components suggested by Lee (1999).

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.75-82
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• 1998

A total of 842 observations (277 in B, 282 in V, and in R) for U Pegasi were made in October of 1996 at Mt. Sobaek Observatory. With our data we constructed the BVR light curves and determinded 5 times of minimum light. We also obtained physical parameters of the system by combined analysis of both light and radial velocity curves using the Wilson-Devinney code.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.31-38
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• 2002

The BVR CCD full light curves of ZZ Aur were obtained as one of the near-contact binary observing programs at the Sobaek Mt. Observatory during Feb. 2000 - Feb. 2001. From the present observations, three primary and seven secondary times of minimum light were obtained. The photometric solutions have been found using the Wilson and Divenny model.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.33-43
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• 1997

New BVR CCD photometric observations of EB type close binary V388 Cyg were obtained at the Sobaeksan Astronomy Observatory during 10 nights from October to December 1995. We analyse new 3 color (B, V & R) light curves simultaneously using the Wilson-Devinney code. Now, it is not yet clear whether V388 Cyg is contact or semidetached system. Published epochs of times of minima to data were used to study the changes in period of the system, and calculated a new light elements with the secular terms, $-4.83{\times}10^{-10}$, which indicated the continuous decrease of the period.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.44-58
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• 1997

The BVR CCD photometric observations of W UMa-type eclipsing binary SS Ari were made on ten nights from November 1996 to December 1996. Eight new times of minimum lights were derived. The analysis of times of minima of SS Ari confirms the suggestions of other previous investigators that the orbital period of SS Ari have been suffering from a sinusoidal varition. The amplitude and period for the cyclic period changes were calculated as about $58^{y}$ and $0.^{d}053$, respectively. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. In the earlier case, the third body has a mass of $1.3M_{\odot}$, if exist, in the form of a white dwarf or a binary system. It seems that the system velocities from the spectroscopic observations supports this interpretation. Meanwhile in the latter case, the primary component is mainly responsible for the magnetic activity of this system with a theoretical amplitude of $\pm0.^{m}08$. However, we cannot make a conclusion which is reasonable explanation at this point, due to lack of observational data. Moreover, the period variation of SS Ari shows duplication about $14^y$, cyclic period with an amplitude of about $0.^d001$ to the above periodic change. We also cannot make an acceptable conclusion for it at this time.