• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.179-182
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• 2015

Dust has recently been found to be prevalent in compact binaries such as non-magnetic Cataclysmic Variable systems. As a possible source of this dust is from solid bodies, we explore impacts to non-magnetic Cataclysmic Variable disks. We use three-dimensional Smoothed Particle Hydrodynamic simulations to search for impact signatures. From injections of whole bodies to these disks, we find pulse shapes in simulated bolometric light curves that resemble impact flashes in the light curves of the Shoemaker-Levy 9 event. As a result, we tentatively identify these light curve shapes as signatures of impacts.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.31.2-31.2
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• 2011

The Vista Variable in the Via Lactea(VVV)는 European Southern Observatory(ESO) Public Survey 중 하나로 Near-IR에서 (주로 K-band)에서 관측되며 1929시간에 걸쳐 은하 중심부의 더 깊은 영역에 대한 관측을 수행할 것이다. VVV Survey를 통해 520 sq. deg에 걸친 영역에서 33개의 잘 알려진 구상성단과 350개의 산개성단을 포함한 ~109개의 별에 대한 광도 곡선을 얻을 수 있을 것으로 예상되며 이들을 분류하기 위해 자동화된 분류 체계가 필요할 것이다. 본 연구는 VVV Survey의 일환으로 보현산 천문대의 근적외선 카메라시스템 KASINICS를 이용하여 Cataclysmic Variable stars에 대한 관측을 시행하고 있다. Cataclysmic Variable stars는 초신성 폭발이나 쌍성계 중 한 쪽 별에서 다른 쪽 별로 대기가 유입되었는 경우 등에 의해 광도가 급격히 증가하는 천체로 아직 많이 연구되지 않은 적외선 파장대로 관측함으로써 적외선영역에서의 물리적 특성에 대한 분석을 하고자 한다. 본 발표에서는 보현산 천문대의 근적외선카메라시스템 KASINICS에서 관측한 결과의 일부를 소개하고자 한다.

• Publications of The Korean Astronomical Society
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• v.15 no.spc1
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• pp.113-118
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• 2000

A magnetic cataclysmic variable has a rotating magnetic white dwarf which accretes matter from its late type companion. Kim & Beuermann (1995) presented a phenomenological model of the accretion from its surrounding structure e.g., a disk into the magnetosphere of the white dwarf, and presented results for the spin modulated X-ray spectrum and light curves. Using this model, we calculate the optical continuum and line emission which result from reprocessing of X-rays in the accretion stream within the magnetosphere. Penning (1985) suggested the observed spin-modulated radial-velocity variations might result from reprocession of X-rays in the disk. We, however, find the radiation can be originated from the magnetosphere accretion stream. We use the same geometrical model to calculate the optical and the X-ray behaviour. The results from the two wavelength bands are internally consistent. We conclude that this approach will increase the diagnostic accuracies of the results.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.169-173
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• 2012

A summary is presented of what is currently known about the surface temperatures of accreting white dwarfs (WDs) detected in non-magnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. A special focus is placed on WD temperatures above and below the CV period gap as a function of the orbital period, $P_{orb}$. The principal uncertainty of the temperatures for the CV WDs in the $T_{eff}-P_{orb}$ distribution, besides the distance to the CV, is the mass of the WD. Only in eclipsing CV systems, an area of eclipsing binary studies, which was so central to Robert H. Koch's career, is it possible to know CV WD masses with high precision.

• Bulletin of the Korean Space Science Society
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• 2000.04a
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• pp.24-24
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• 2000

No Abstract, See Full Text

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.193-195
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• 2015

The Palomar Transient Factory is a project making use of a Schmidt 48 inch telescope located on the Palomar Mountain, which is surveying the sky with dynamical cadences. It was deployed in 2009 and the observed sky region is over 1200 square degrees. We have studied the long-term periodic variabilities of the known galactic cataclysmic variables (CVs). More than 20 of the sources had been found to have long term periodic signals, ranging from several tens of days to several hundreds of days. Some possible scenarios are proposed to explain the results, such as a magnetic field change of the companion star, precession of the accretion disk, triple systems and superoutburst cycles. Some preliminary discussion will be presented in this article.

• Journal of Astronomy and Space Sciences
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• v.34 no.1
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• pp.37-44
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• 2017

In this paper, analysis results of the photometric data of DO Dra will be presented. DO Dra had been observed with 1 m LOAO telescope and 0.6 m CBNUO telescope from 2005 through 2014. The data shows kind of periodic oscillation behavior in the orbital period and also in the spin period. It has been found that these QPOs are not observed always and that the periods vary from 30 min to 80 min. We also found that the period variation seems to repeat itself with the period of 13.5 days. It is essential to monitor this object in the future as well as to carry out model calculation in order to have better understanding of these QPO phenomena.

• Journal of Astronomy and Space Sciences
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• v.36 no.4
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• pp.283-292
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• 2019

The purpose of this study was to develop a period analysis algorithm for detecting new variable stars in the time-series data observed by charge coupled device (CCD). We used the data from a variable star monitoring program of the CBNUO. The R filter data of some magnetic cataclysmic variables observed for more than 20 days were chosen to achieve good statistical results. World Coordinate System (WCS) Tools was used to correct the rotation of the observed images and assign the same IDs to the stars included in the analyzed areas. The developed algorithm was applied to the data of DO Dra, TT Ari, RXSJ1803, and MU Cam. In these fields, we found 13 variable stars, five of which were new variable stars not previously reported. Our period analysis algorithm were tested in the case of observation data mixed with various fields of view because the observations were carried with 2K CCD as well as 4K CCD at the CBNUO. Our results show that variable stars can be detected using our algorithm even with observational data for which the field of view has changed. Our algorithm is useful to detect new variable stars and analyze them based on existing time-series data. The developed algorithm can play an important role as a recycling technique for used data

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.9-12
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• 2011

Results of an analysis of 11 nights of R-filter CCD photometry data of an intermediate polar MU Camelopardalis (MU Cam) obtained at the Korean 1.0 m telescope at Mt. Lemmon are reported. After checking the spin period with our data, $P_{spin}=0.^d01373801(59)$, we compiled the reported data of maxima timing and an O-C diagram analysis has been carried out to understand the spin period variation. A significant spin period variation was detected, and fitting the O-C points to a cubic parabola led to an ephemeris of $BJD_{max}=2453682.4178(94)+0.0137380(13)E-2.07(55){\times}10^{-11}E^2+2.28(52){\times}10^{-15}E^3$. The torque experienced by the magnetic compact star accreting in a disk is estimated as ${\tau}{\approx}1.815{\times}10^{35}gcm^2/s^2$ in a simple approximation in order to show how important monitoring the period variation is. Thus we conclude that monitoring the long-term spin period variation will help to understand the physical condition of magnetic compact stars.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.143-152
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• 2006

An automatic observation system has been constructed at Chungbuk National University for the purpose of monitoring the bright and long period variable stars effectively. We improved the control part of 40cm telescope of the LX200 and developed n observing software ObsTool II so that the telescope, CCD camera and dome can be controlled in one software. ObsTool II is a COM (Common Object Module) based software, which can be easily reprogrammed in case that a new telescope or CCD camera is installed. Because this system has an additional function in which the telescope can switch the variable, comparison, and check stars respectively as like a photoelectric observation, we can observe the variable star even if the CCD view field does not contain the comparison star with the variable star. In order to check the system stability a W UMa type variable V523 Cas and a magnetic cataclysmic variable TT Ari have been observed with the constructed system and the results have been discussed in context with the possibility of a further application of our automatical observation system.