A5084930890- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Spacecraft and Cryogenic Technologies
- High-pressure geophysics and materials
- Scientific Measurement and Uncertainty Evaluation
- History and Developments in Astronomy
- Advanced X-ray Imaging Techniques
- Medical Imaging Techniques and Applications
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- Cognitive Computing and Networks
- Geomagnetism and Paleomagnetism Studies
- Optical Systems and Laser Technology
- Material Science and Thermodynamics
- Molecular Spectroscopy and Structure
- Astronomical and nuclear sciences
- Robotics and Automated Systems
Gongju National University of Education
2023
Kongju National University
2023
Chungnam National University
2009-2022
Kyungpook National University
2022
Korea Astronomy and Space Science Institute
2007-2018
Osservatorio Astrofisico di Catania
2009
University of Catania
2009
Indian Institute of Astrophysics
2009
University of Crete
2009
Chungbuk National University
2004
Measuring solar-like oscillations in an ensemble of stars a cluster, holds promise for testing stellar structure and evolution more stringently than just fitting parameters to single field stars. The most-ambitious attempt pursue these prospects was by Gilliland et al. who targeted 11 turn-off the open cluster M67 (NGC 2682), but oscillation amplitudes were too small (<20 μmag) obtain unambiguous detections. Like we also aim at detecting M67, target red giant with expected range 50–500 μmag...
We present the physical properties of V404 Lyr exhibiting eclipse timing variations and multiperiodic pulsations from all historical data including Kepler observations. Detailed analyses 2,922 minimum epochs showed that orbital period has varied through a combination with an upward-opening parabola two sinusoidal variations, periods $P_3$=649 d $P_4$=2,154 semi-amplitudes $K_3$=193 s $K_4$=49 s, respectively. The secular increase could be interpreted as secondary to primary mass transfer...
Among quadruples or higher multiplicity stars, only a few doubly eclipsing binary systems have been discovered. They are important targets for understanding the formation and evolution of multiple stellar because we can obtain accurate parameters from photometric spectroscopic studies. We present observational results this kind rare object, 1SWASP J093010.78+533859.5, which feature had detected previously SuperWASP archive. Individual point-spread function photometry two objects with...
Abstract We present the results from a detailed analysis of our time-series spectroscopic observations and Transiting Exoplanet Survey Satellite (TESS) photometric data eclipsing binary V389 Cas. The radial velocities (RVs) primary faint secondary components were obtained total 61 high-resolution spectra made between 2016 2019. disentangling used to determine effective temperature projected rotational velocity star based on χ 2 fitting statistic, yielding T eff,1 = 7720 ± 200 K <mml:math...
KIC 9532219 is a W UMa-type eclipsing binary with an orbital period of 0.1981549 d that below the short-period limit ($\sim$0.22 d) distribution for contact binaries. The {\it Kepler} light curve system exhibits striking changes in both eclipse depths and maxima. Applying third-body spot effects, light-curve synthesis indicates pair currently marginal stage mass ratio $q$=1.20, inclination $i$=66.0 deg, temperature difference $\Delta$ ($T_{1}$--$T_{2}$)=172 K, third $l_3$=75.9 \%. To...
We present the physical properties of semi-detached Algol-type eclipsing binary Y Cam based on high resolution spectra obtained using Bohyunsan Optical Echelle Spectrograph. This is first spectroscopic monitoring data for this interesting system, which has a δ Sct-type pulsating component. total 59 over 14 nights from 2009 December to 2011 March. Double-lined spectral features hot primary and cool secondary components were well identified. determined effective temperatures two stars be...
We have made an asteroseismic analysis of the variable blue stragglers in open cluster M67. The data set consists photometric time series from eight sites using nine 0.6-2.1 meter telescopes with a baseline 43 days. In two stars, EW Cnc and EX Cnc, we detect highest number frequencies (41 26) detected delta Scuti stars belonging to stellar cluster, has second any star. computed grid pulsation models that take effects rotation into account. distribution observed theoretical show wide...
We present four new transits of the planetary system TrES-3 observed between 2009 May and 2010 June. Among these, third transit by itself indicates possible evidence for brightness disturbance, which might be result planet blocking a cool starspot on stellar surface. A total 109 times, including our measurements, were used to determine improved ephemeris with epoch 2454185.910944$\pm$0.000072 HJED an orbital period 1.30618700$\pm$0.00000015 d. analyzed light curves using JKTEBOP code...
We present both binarity and pulsation of KIC 6220497 from the Kepler observations. The light curve synthesis shows that eclipsing system is a semidetached Algol with parameters q = 0.243 ± 0.001, i 77.3 0.3 deg, ΔT 3372 58 K, in which detached primary component fills its Roche lobe by ∼87 per cent. A multiple frequency analysis eclipse-subtracted residuals reveals 33 frequencies range 0.75–20.22 d−1 amplitudes between 0.27 4.56 mmag. Among these, four are fundamental (f1, f5) p (f2, f7)...
Abstract This study presents the high-resolution spectra of eclipsing binary AB Cas with a δ Sct-type pulsating component, which were obtained using Bohyunsan Optical Echelle Spectrograph in Korea. In this paper, radial velocities for primary and secondary stars measured from total 27 made during two nights 2015 October. We derived accurate physical properties system first time by simultaneously analyzing our velocity curves together previously published uvby light curves. Individual masses,...
We present the first high-resolution spectra for eclipsing binary V404 Lyr showing $\gamma$ Dor pulsations, which we use to study its absolute properties. By fitting models disentangling spectrum of primary star, found that it has an effective temperature $T_{\rm eff,1}=7,330 \pm 150$ K and a rotational velocity $v_1\sin$$i=148\pm18$ km s$^{-1}$. The simultaneous analysis our double-lined radial velocities pulsation-subtracted ${\it Kepler}$ data gives us accurate stellar system parameters...
The Kepler light curve of KIC 4739791 exhibits partial eclipses, the inverse O'Connell effect, and multiperiodic pulsations. Including a starspot on either binary components, light-curve synthesis indicates that is in detached or semi-detached configuration with both short orbital period low mass ratio. Multiple frequency analyses were performed residuals after subtracting binarity effects from original data. We detected 14 frequencies: 6 low-frequency region (0.1−2.3 days−1) 8...
We report the first $BV$ light curves and high-resolution spectra of post-mass transfer binary star WASP 0131+28 to study absolute properties extremely low-mass white dwarfs. From observed spectra, double-lined radial velocities were derived, effective temperature rotational velocity brighter, more massive primary found be $T_{\rm eff,1} = 10,000 \pm 200$ K $v_1\sin$$i$ 55 $\pm$ 10 km s$^{-1}$, respectively. The combined analysis {\it TESS} archive data ours yielded accurate fundamental...
Oscillating Algol-type eclipsing binaries (oEA) are very interesting objects that have three observational features of eclipse, pulsation, and mass transfer. Direct measurement their masses radii from the double-lined radial velocity data photometric light curves would be most essential for understanding evolutionary process performing asteroseismological study. We present physical properties oEA star XX Cep high-resolution time-series spectroscopic data. The effective temperature primary...
<i>Context. <i/>Rotation and magnetic activity are intimately linked in main-sequence stars of G or later spectral types. The presence level depend on stellar rotation, rotation itself is strongly influenced by the strength topology fields. Open clusters represent especially useful targets for investigating connection among activity, age. Over time, evolve, providing us with a promising diagnostic tool to determine age field stars.<i>Aims. <i/>The open cluster M11 has been studied as part...
OO Dra is a short-period Algol system with $\delta$ Sct-like pulsator. We obtained time-series spectra between 2016 February and May to derive the fundamental parameters of binary star study its evolutionary scenario. The radial velocity (RV) curves for both components were presented, effective temperature hotter more massive primary was determined be $T_{\rm eff,1}$ = 8260 $\pm$ 210 K by comparing disentangling spectrum Kurucz models. Our RV measurements solved $BV$ light Zhang et al....
We examined light curves of 1138 stars brighter than 18.0 mag in the I band and less a mean magnitude error 0.1 V from Optical Gravitational Lensing Experiment (OGLE)-III eclipsing binary catalogue, found 90 new systems exhibiting apsidal motion. In this study, samples motion Small Magellanic Cloud (SMC) were increased by factor about 3.0 previously known. order to determine period for binaries, we analysed detail both eclipse timings using MACHO (MAssive Compact Halo Objects) OGLE...
Abstract We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely (EMP; –3.0) candidates from the Sloan Digital Sky Survey Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. find 10 EMP stars among our candidates, we newly identify three carbon-enhanced with [Ba/Fe] 0. Although chemical VMP/EMP generally follow overall...
Time-series CCD photometric observations of the intermediate-age open cluster NGC 2099 were performed to search for variable stars. We also carried out BV photometry study physical properties variables in cluster. Using V-band time-series data, we carefully examined light variations about 12,000 stars range 10 < V 22 mag. A total 24 have been identified; seven are previously known and 17 newly identified. On basis observational such as curve shape, period, amplitude, classified new nine...
We report the photometry of KIC 11401845 displaying multiperiodic pulsations, superimposed on binary effects. Light-curve synthesis shows that star is a short-period detached system with very low mass ratio q = 0.070 and filling factors F1 45% F2 99%. Multiple-frequency analyses were applied to light residuals after subtracting synthetic eclipsing curve from observed data. detected 23 frequencies signal-to-noise ratios larger than 4.0, which orbital harmonics (f4, f6, f9, f15) in...
Abstract We present the Transiting Exoplanet Survey Satellite (TESS) photometry and our high-resolution spectra of EL CVn–type star 1SWASP J084356.46–113327.5 (WASP 0843–11), which consists an F-type main-sequence (MS) a hotter low-mass helium white dwarf precursor (pre-He WD). In spectral analysis, double-lined radial velocities (RVs) were obtained for first time. From simultaneous analysis TESS light RV curves, masses, radii, temperatures each component determined to be M 1 = 1.733 ± 0.031...
We present evidence that multiple accretion events are required to explain the origin of $Gaia$-Sausage and Enceladus (GSE) structures, based on an analysis dynamical properties main-sequence stars from Sloan Digital Sky Survey Data Release 12 $Gaia$ 2. GSE members selected have eccentricity ($e$) $>$ 0.7 [Fe/H] $<$ -1.0, separated into low high orbital-inclination (LOI/HOI) groups. find LOI mainly $e < 0.9$ clearly separable two groups with prograde retrograde motions. The exhibit motions...
We report on an ambitious multisite campaign aimed at detecting stellar variability, particularly solar-like oscillations, in the red giant stars open cluster M67 (NGC 2682). During six-week observing run, which comprised 164 telescope nights, we used nine 0.6-m to 2.1-m class telescopes located around world obtain uninterrupted time series photometry. outline here data acquisition and reduction, with emphasis optimization of signal-to-noise ratio low-amplitude (50–500 μmag) oscillations....
We present the results of a multi-site photometric campaign carried out in 2004–2008 for Algol-type eclipsing binary system CT Her, primary component which displays δ Scuti-type oscillations. Our data consist differential light curves collected filters B and V, were analysed using method Wilson-Devinney (Phoebe). After identifying an adequate model removing best-fit light-curve solution, we performed Fourier analysis residual V to investigate pulsational behaviour. confirm presence rapid...
Abstract We present the results from a detailed analysis of our high-resolution spectra and historical photometric observations semidetached eclipsing binary V392 Ori with δ Scuti ( Sct) pulsating component. A total 31 spectroscopic were carried out at both Bohyunsan Optical Astronomy Observatory in Korea Thai National Thailand during 2016 2017 observing seasons. The radial velocities (RVs) primary faint secondary components determined, effective temperature projected rotational velocity...