• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.231-232
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• 2015

R Canis Majoris is a bright, short-period ($1^d$.1359) Algol-type eclipsing binary. For a long time, it was considered to be a low-mass binary star with $M_1=1.1M_{\odot}$ and $M_2=0.17M_{\odot}$ primary and secondary components, respectively (Tomkin, 1985). Glazunova, Yushchenko & Mkrtichian (2009) found new masses for the primary and secondary components of $M_1=1.81M_{\odot}$ and $M_2=0.23M_{\odot}$, respectively and resolved a long-standing problem with the low masses of components for this binary. Budding and Butland (2011) confirmed the results of Glazunova, Yushchenko & Mkrtichian and obtained improved orbits and masses. New spectroscopic observations of R CMa were done during 8 nights on December 2012 with the 2.4-meter telescope of the Thai National Observatory (TNO) and fibre-fed medium resolution echelle spectrograph. We obtained new, accurate orbital radial velocities of the two components of this binary system. Results of these investigations and the new orbital parameters are presented.

• Journal of The Korean Astronomical Society
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• v.53 no.2
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• pp.43-48
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• 2020

We report an analysis of two poorly studied eclipsing binary stars, GSC 04396-00605 and GSC 04395-00485 (recently named V455 Dra and V454 Dra, respectively). Photometric data of the two stars were obtained using the 1-m Korean telescope of the LOAO operated by KASI while monitoring the cataclysmic variable DO Dra in the frame of the Inter-Longitude Astronomy (ILA) project. We derived periods of 0.434914 and 0.376833 days as well as initial epochs JD 2456480.04281 and JD 2456479.0523, respectively, more accurate than previously published values by factors 9 and 6. The phenomenological characteristics of the mean light curves were determined using the New Algol Variable (NAV) algorithm. The individual times of maxima/minima (ToM) were determined using the newly developed software MAVKA, which outputs accurate parameters using "asymptotic parabola" approximations. The light curves were approximated using phenomenological and physical models. In the NAV algorithm, the phenomenological parameters are well determined. We derived physical parameters using the Wilson-Devinney model. In this model, the best-fit parameters are highly correlated, thus some of them were fixed to reasonable values. For both systems, we find evidence for the presence of a cool spot and estimate its parameters. Both systems can be classified as overcontact binaries of EW type.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.34.4-35
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• 2021

We present the TESS photometry and our high-resolution spectra of the semi-detached Algol EW Boo. For an orbital period study, we collected all available times of minima including ours for the last 30 years. It is found that the eclipse timing variation of the system can be represented by a periodic oscillation of 18.5±1.0 yr plus a secular period increase with a rate of [dP/dt]_orb=-6(±3)×10^-8 d yr^-1. From our observed spectra, the effective temperature of the primary star was determined to be T_eff,1=8560±118 K. From a simultaneous analysis of the TESS light and our double-lined radial velocity curves, the absolute masses, radii, and luminosities are M₁=2.30±0.07M_⊙, M₂=0.38±0.01M_⊙, R₁=1.92±0.02 R_⊙, R₂=1.27±0.01 R_⊙, L₁=1.92±0.02 L_⊙, and L₂=0.752±0.007 L_⊙, respectively. Multiple frequency analyses were carried out for the light residuals after subtracting the binary star model. We detected a total of 75 frequencies in the region of 16.50-104.8 day-1. Our results demonstrate that the more hotter primary star of EW Boo is a δ Sct pulsator by considering its position in the δ Scuti region of the Cepheid instability strip and pulsational characteristics.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.71.1-71.1
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• 2013

Among quadruples or higher multiplicity stars, only a few binary systems have been discovered. They are important targets to understand the formation and evolution of multiple stellar systems because we can obtain accurate stellar parameters from photometric and spectroscopic studies. We present the observational results of this kind of rare object 1SWASP J093010.78+533859.5, for which the doubly eclipsing feature had been detected previously from the SuperWASP photometric archive. Individual PSF photometry for two objects with a separation of about 1.9 arcsec was performed for the first time in this study. Our time-series photometric data show that the brighter object A is an Algol-type detached eclipsing binary with an orbital period of 1.3 days and the fainter B is a W UMa-type contact eclipsing binary with a period of 0.23 days. Using the high-resolution optical spectra, we obtained well-defined radial velocity variations of the system A. Furthermore, stationary spectral lines were detected and should have originated from the other stellar component, which was confirmed by the third object contribution from the light curve analysis. No spectral feature of the system B was detected, probably due to its faintness. We obtained the binary parameters and the absolute dimensions from each light curve synthesis. The primary and secondary components of the system A have a spectral type of K1 and K5 main sequences, respectively. Two components of system B have nearly the same type of K3 main sequence. Light variations at out of eclipses were appeared in both systems, interpreting as the effect of stellar spots on these late spectral type stars. We estimated the distances to the systems A and B individually. They may have similar distances of about 70 pc and seem to be gravitationally bound with a separation of about 130 AU. In conclusion, we suggest that 1SWASP J093010.78+533859.5 is a quintuple stellar system with a hierarchical structure of a triple system A(ab)c and a binary system B(ab).

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.185-196
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• 2016

New multiband BVRI light curves of NSVS 1461538 were obtained as a byproduct during the photometric observations of our program star PV Cas for three years from 2011 to 2013. The light curves indicate characteristics of a typical W-subtype W UMa eclipsing system, displaying a flat bottom at primary eclipse and the O'Connell effect, rather than those of an Algol/b Lyrae eclipsing variable classified by the northern sky variability survey (NSVS). A total of 35 times of minimum lights were determined from our observations (20 timings) and the SuperWASP measurements (15 ones). A period study with all the timings shows that the orbital period may vary in a sinusoidal manner with a period of about 5.6 yr and a small semi-amplitude of about 0.008 day. The cyclical period variation can be interpreted as a light-time effect due to a tertiary body with a minimum mass of 0.71 M_⊙. Simultaneous analysis of the multiband light curves using the 2003 version of the Wilson-Devinney binary model shows that NSVS 1461538 is a genuine W-subtype W UMa contact binary with the hotter primary component being less massive and the system shows a low mass ratio of q(m_c/m_h)=3.51, a high orbital inclination of 88.7°, a moderate fill-out factor of 30 %, and a temperature difference of ΔT=412 K. The O'Connell effect can be similarly explained by cool spots on either the hotter primary star or the cool secondary star. A small third-light corresponding to about 5 % and 2 % of the total systemic light in the B and V bandpasses, respectively, supports the third-body hypothesis proposed by the period study. Preliminary absolute dimensions of the system were derived and used to look into its evolutionary status with other W UMa binaries in the mass-radius and mass-luminosity diagrams. A possible evolution scenario of the system was also discussed in the context of the mass vs mass ratio diagram.