• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.15-15
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• 1992

AQ Cassiopeiae (BD+61`0242, uv=10, Sp=B3+Bg) is a totally eclipsing binary system with the obital period of about 12 days. 71 was observed for 15 nights in 1985 with the1.8-m telescope at the DAO, employing a Reticon and a three-stage image tube attached to the spectrograph. And also, photometric observations of AQ Cas had been made inUBv for six years from 1982 to 1988 at Yonsei University Observatory(YUO). This work includes UBV observations obtained at YUO as a part of The Ten-Year Observing Program(1982-1992). Double lined radial, velocity curves and Ufv light curves of AQC as are constructed. The light curves and radial velocity curves show a strong evidence of circumstellar matter or mass stream. It is clear at the phases of just outside externaleclipse contacts, particularly at phase 0.8-0.9, shown in Figures 1 and 2. A solution by combining the radial velocity and photometric curves of the binary was obtained with the Wilson-Devinney Code. We found that the system is semi-detached with the coolcomponent filling its Roche lobe. The absolute dimensions of AQ Cas are calculated. The result shows that this system consists of two massive and subgiant stars.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.47-49
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• 2012

Massive binary stars lose mass by two mechanisms: jet-driven mass loss during periods of active mass transfer and by wind-driven mass loss. Beta Lyrae is an eclipsing, semi-detached binary whose state of active mass transfer provides a unique opportunity to study how the evolution of binary systems is affected by jet-driven mass loss. Roche lobe overflow from the primary star feeds the thick accretion disk which almost completely obscures the mass-gaining star. A hot spot predicted to be on the edge of the accretion disk may be the source of beta Lyrae's bipolar outflows. I present results from spectropolarimetric data taken with the University of Wisconsin's Half-Wave Spectropolarimeter and the Flower and Cook Observatory's photoelastic modulating polarimeter instrument which have implications for our current understanding of the system's disk geometry. Using broadband polarimetric analysis, I derive new information about the structure of the disk and the presence and location of a hot spot. These results place constraints on the geometrical distribution of material in beta Lyrae and can help quantify the amount of mass lost from massive interacting binary systems during phases of mass transfer and jet-driven mass loss.

• Journal of Astronomy and Space Sciences
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• v.31 no.3
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• pp.187-197
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• 2014

We have investigated the dynamical stability of the proposed companions orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al. 2010). The two candidate companions are of stellar to substellar nature, and were inferred from timing measurements of the system's primary and secondary eclipses. We applied well-tested numerical techniques to accurately integrate the orbits of the two companions and to test for chaotic dynamical behavior. We carried out the stability analysis within a systematic parameter survey varying both the geometries and orientation of the orbits of the companions, as well as their masses. In all our numerical integrations we found that the proposed SW Lyn multi-body system is highly unstable on time-scales on the order of 1000 years. Our results cast doubt on the interpretation that the timing variations are caused by two companions. This work demonstrates that a straightforward dynamical analysis can help to test whether a best-fit companion-based model is a physically viable explanation for measured eclipse timing variations. We conclude that dynamical considerations reveal that the proposed SW Lyncis multi-body system most likely does not exist or the companions have significantly different orbital properties from those conjectured in Kim et al. (2010).

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.21-30
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• 1999

We perform CCD observations in VRI filters for AK Her during 3 nights in Feb 1997 and Mar 1998 at Mt. Sobaek National Observatory, and obtained 236 images in V, 198 in R, and 197 in I filter. From the data, we construct light curves which contain a pair primary and secondary minima and (O-C) diagram. We analyzed the obtained light curves of AK Her using the Wilson-Devinney code. From the analyses, we find that AK Her is more likely detached or semi-detached than contact system. From the (O-C) diagram, we find that the (O-C) residuals increases out of accordance with the expectation of Borkovits & Hegedus since 1990. However, we cannot identify cause of the periodic variation of the (O-C) residuals.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.249-260
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• 2003

CCD photometric observations of a W UMa type contact binary AH Cnc were performed for ten nights from December 1998 to May 1999 using a PM512 CCD camera and BVI filters attached to the 61㎝ reflector at Sobaeksan Optical Astronomy Observatory. New BVI light curves were analyzed with contact Mode 3 of the Wilson-Devinney binary model. We obtained photometric solutions and Roche geometry of this binary system. Through the analysis of the (O-C) diagram with all times of minimum light published so far and including hour's secular variations of orbital period and the mass transfer rate were calculated.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.261-268
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• 2003

CCD observations of times of minimum light of IQ Per with apsidal motion were made in VR bandpasses for four nights from November to December, 2002. From the observations four times of minimum light were determined. All times of minimum light collected from literatures, including ours, were analyzed to determine the apsidal motion parameters of IQ per. The sidereal and apsidal motion periods were calculated to be $0.^{s}035$ and $0.^{y}2$ slightly longer than those of Degirmenci (1997), respectively. The apsidal motion parameters of IQ Per derived in this paper show good agreement with Degirmenci's values. Our results support his internal density constant of $k_{2obs}$ = 0.0038 for IQ Per and 5 % accuracy of agreement between the observed and modelled values of the apsidal motion constant.

• Publications of The Korean Astronomical Society
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• v.9 no.1
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• pp.101-110
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• 1994

We have investigated intensively an optical telescope with 76cm diameter and CCD camera system in astronomical observatory of Kyung Hee university, in order to maximize instrumental functions of our observational equipments and to construct a more reliable photometric system. And computer softwares AUTO DOME, KH CCD and KH PHO for astronomical image observations and their automatic photometries with high accuracy have been made for observers w use our observational system conveniently and efficiently. Throughout careful examinations of these programs, it has been proved that the observing time by our program is shorter than that by manual operations, so that, fast and accurate observations can be executed with ease. For open cluster NGC 7063 observed with S/N value of 350 or more by KH PHO, we have found the magnitude measurements of 11 object stars would show 0.007 magnitude difference, comparing with magnitude data from IRAF/APPHOT. From automatic photometry of eclipsing binary, AB And observed by our software, total 220 data points with good quality have been acquired during 8 hours and so we could make a better light curve than that obtained from any observational results by domestic photoelectric photometry system.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.76.2-76.2
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• 2010

We present the final results of our study on the mass-loss rate of donor stars in cataclysmic variables (CVs). Observed donors are oversized in comparison with those of isolated single stars of the same mass, which is thought to be a consequence of the mass loss. Using the empirical mass-radius relation of CVs and the homologous approximation for changes in effective temperature T2, orbital period P, and luminosity of the donor with the stellar radius, we find the semi-empirical mass-loss rate M2dot of CVs as a function of P. The derived M2dot is at ~10-9.5-10-10 $M\odot$/yr and depends weakly on P when P > 90 min, while it declines very rapidly towards the minimum period when P < 90 min. The semi-empirical M2dot is significantly different from, and has a less-pronounced turnaround behavior with P than suggested by previous numerical models. The semi-empirical P-M2dot relation is consistent with the angular momentum loss due to gravitational wave emission, and strongly suggests that CV secondaries with 0.075 $M\odot$ < M2 < 0.2 $M\odot$ are less than 2 Gyrs old. When applied to selected eclipsing CVs, our semi-empirical mass-loss rates are in good agreement with the accretion rates derived from the effective temperatures T1 of white dwarfs. Based on the semi-empirical M2dot, SDSS 1501 and 1433 systems that were previously identified as post-bounce CVs have yet to reach the minimal period.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.70.1-70.1
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• 2018

The DEEP-South photometric census of small Solar System bodies is producing massive time-series data of variable, transient or moving objects as a by-product. To fully investigate unexplored variable phenomena, we present an application of multi-aperture photometry and FastBit indexing techniques to a portion of the DEEP-South year-one data. Our new pipeline is designed to do automated point source detection, robust high-precision photometry and calibration of non-crowded fields overlapped with area previously surveyed. We also adopt an efficient data indexing algorithm for faster access to the DEEP-South database. In this paper, we show some application examples of catalog-based variability searches to find new variable stars and to recover targeted asteroids. We discovered 21 new periodic variables including two eclipsing binary systems and one white dwarf/M dwarf pair candidate. We also successfully recovered astrometry and photometry of two near-earth asteroids, 2006 DZ169 and 1996 SK, along with the updated properties of their rotational signals (e.g., period and amplitude).

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.181-188
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• 2000

DO Cas is a short period (P=0.68day) eclipsing binary star and is classified as a near-contact binary by Shaw(1990). There is no published radial velocity curve for this short period binary after Mannino(1958). Hill(1991) suspected that Mannino's radial velocity curve had some serious mistake. So, we scanned the original plates used by Mannino with PDS and the spectra were employed to IRAF packages to estimate the radial velocities. The radial velocity curve and the BVR light curves made by us in 1998 were analyzed simultaneously with Wilson-Devinney code. We found that DO Cas is a contact or near-contact binary which the primary component fills its Roche lobe and we also estimated the absolute dimensions of each components of this system.