• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.75-86
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• 2019

UV Psc is a typical RS CVn type system undergoing dynamic chromosphere activity. We performed photometric observations of the system in 2015 and secured new BVR light curves showing well-defined photometric waves. In this paper, we analyzed the light curves using Wilson-Devinney binary code and investigated the orbital period of the system. The combination of our light curve synthesis with the spectroscopic solution developed by previous investigators yielded the absolute parameters as: $M_1=1.104{\pm}0.042M_{\odot}$, $R_1=1.165{\pm}0.025R_{\odot}$, and $L_1=1.361{\pm} 0.041L_{\odot}$ for the primary star, and $M_2=0.809{\pm}0.082M_{\odot}$, $R_2=0.858{\pm}0.018R_{\odot}$, and $L_2=0.339 {\pm}0.010L_{\odot}$ for the secondary star. The eclipse timing diagram for accurate CCD and photoelectric timings showed that the orbital period may vary either in a downward parabolic manner or a quasi-sinusoidal pattern. If the latter is adopted as a probable pattern for the period change, a more plausible account for the cyclic variation may be the light time effect caused by a circumbinary object rather than an Applegate-mechanism occurring via variable surface magnetic field strengths.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.42.2-42.2
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• 2014

We investigate the history of formation of ~400 galaxies in four Abell clusters at 0.04

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.55.3-55.3
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• 2016

By comparing MIRIS Paschen-${\alpha}$ ($Pa{\alpha}$) Galactic Plane Survey (MIPAPS) data with Anderson's H II region catalog (the most complete Galactic H II region catalog up to date), we confirmed $Pa{\alpha}$ detections from ~50% of the H II region candidates in Cepheus (Galactic longitude from $+96^{\circ}$ to $116^{\circ}$). The detection of the hydrogen recombination line identifies these candidates as clear H II regions. If we extend this result to the whole plane, more than 1000 candidates are expected to be identified as H II regions. In this contribution, we present the results of quantitative estimations (brightness, size, etc.) for the $Pa{\alpha}$ blobs detected in Cepheus. To obtain intensity of $Pa{\alpha}$ emission line, we perform background and point spread function (PSF) matching between two filter images (line and continuum filters) as well as flux calibration.

• Journal of Astronomy and Space Sciences
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• v.40 no.1
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• pp.19-27
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• 2023

We present the results of using small telescopes in the United Arab Emirates (UAE) for observing variable stars and asteroids. Two telescopes, namely, 5" apochromatic refractor and 14" Schmidt-Cassegrain, at Al-Khatim Observatory (M44) were used for the observations. The targets were the three variable stars RR GEM, AG LMi, and DL CMi and the asteroid 22 Kalliope. We found a good consistency between our light curves and published ones for the calibration targets, i.e., the asteroid 22 Kalliope and the variable star RR GEM. According to previous studies, AG LMi has two suggested periods, 16.3 hours and 32.62 hours. Our results clearly confirm the second one, with a period of 32.6175 hours. The star DL CMi has several suggested periods as per previous studies, such as 4.0173 days, 1.9606 days, and 2.0086 days. Our observations confirm the first one, with a period of 4.0159 days. These results demonstrate the effectiveness of using small telescopes for observing variable stars and asteroids. This work provides some recommendations on using small telescopes for such observations.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.58.2-58.2
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• 2015

We present a library of high spectral resolution (R ~ 40,000) and high signal-to-noise ratio (S/N ~ 200) near-infrared spectra of ~50 late-type stars. The spectra of late-type stars were obtained with Immersion GRating INfrared Spectrograph (IGRINS) covering the full H and K band. The stars are mainly from MK standard stars which have well-defined spectral types and luminosity classes and cover wide ranges of effective temperatures and surface gravities. The spectra are corrected for telluric absorption lines and absolutely flux calibrated using the Two Micron All Sky Survey (2MASS) photometry. In this work, we present the preliminary results of spectroscopic diagnostics for stellar physical parameters. Our ultimate goal is to provide a library of near-infrared spectra of standard stars, which covers all spectral types and luminosity classes, with a high spectral resolution and high signal-to-noise ratio.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.283-287
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• 2015

Within the context of the hugely successful SAGE-LMC and SAGE-SMC surveys, Spitzer photometry observations of the Large and Small Magellanic Clouds have revealed millions of infrared point sources in each galaxy. The brightest infrared sources are generally dust producing and mass-losing evolved stars, and several tens of thousands of such stars have been classified. After photometrically classifying these objects, the dust production by several kinds of evolved stars - such as Asymptotic Giant Branch stars and Red Supergiants - can be determined. SAGE-Spec is the spectroscopic follow-up to the SAGE-LMC survey, and it has obtained Spitzer-IRS $5-40{\mu}m$ spectroscopy of about 200 sources in the LMC. Combined with archival data from other programs, observations at a total of ~1000 pointings have been obtained in the LMC, while ~250 IRS pointings were observed in the SMC. Of these, a few hundred pointings represent dust producing and mass-losing evolved stars, covering a range in colors, luminosities, and thus mass-loss rates. Red Supergiants and O-rich and C-rich AGB stars - the main dust producers - are well represented in the spectroscopic sample. This paper will summarize what we know about the mineralogy of dust producing evolved stars, and discuss their relative importance in the total dust budget.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.367-373
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• 2012

The first all-sky mid-/far-infrared survey by IRAS in the 1980s, has been followed by only two more, by AKARI, from 2006, and WISE in 2010. I discuss some features of the WISE survey, and highlight some key results from early extragalactic observations that have been made by the science team during the operation of the telescope, and the post-operation proprietary period during which the public release data products were being generated. The efficient survey strategy and very high-data rate from WISE produced a catalogue of 530 million objects that was released to the public in March 2012. The WISE survey strategy naturally provided the deepest coverage at the ecliptic poles, where matched comparison fields were obtained using Spitzer, and where AKARI also observed deep fields. I describe some of the follow-up work that has been carried out based on the WISE survey, and the prospects for enhancing the WISE data by combining the AKARI survey results are also discussed. While the all-sky AKARI survey is less deep than the WISE catalogue, and is still being worked on by the AKARI science team, it includes a larger number of bands, extends to longer wavelengths, and in particular has very complementary band passes to WISE in the mid-infrared waveband, which will provide enhanced spectral information for relatively bright targets.

• Publications of The Korean Astronomical Society
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• v.31 no.3
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• pp.43-56
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• 2016

Through time-series BV CCD photometry of the open cluster NGC 225 region, we have detected 30 variable stars including 22 new ones. They are five ${\delta}$ Scuti-type variable stars, a slowly pulsating B star, six eclipsing binary stars and 18 semi-long periodic or slow irregular variables, respectively. We have performed multiple-frequency analysis to determine pulsation frequencies of the ${\delta}$ Scuti-type stars and a slowly pulsating B star, using the discrete Fourier transform and linear least-square fitting methods. We also have derived the periods and amplitudes of 6 eclipsing binaries and a long-period variable star from the phase fitting method, and presented the light curves of all variable stars. A slowly pulsating B star is a member of NGC 225, but ${\delta}$ Scuti-type stars are not members from the positions in the color-magnitude diagram and the radial distancies from the center of the cluster. From Dias et al. (2014, A&A, 564, 79), only three variable stars including the slowly pulsating B star are members of clusters: two are in NGC 225 and one is in Stock 24. But a variable star in Stock 24 is not a member of the cluster because of its position of color-magnitude diagarm.

• Journal of The Korean Astronomical Society
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• v.55 no.3
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• pp.75-86
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• 2022

The lunar surface progressively darkens and reddens as a result of sputtering from solar wind particles and bombardment of micrometeoroids. The extent of exposure to these space weathering agents is frequently calculated as the location in a diagram of reflectance at 750 nm vs. 950 nm/750 nm color (R-C). Sim & Kim (2018) examined the R-C trends of pixels within ~3,500 craters, and revealed that the length (L) and skewness (s) of R-C trends can be employed as a secondary age or maturity indicator. We broaden this research to general lunar surface areas (3,400 tiles of 0.25° × 0.25° size) in 218 mare basalt units, whose ages have been derived from the size-frequency distribution analysis by Hiesinger et al. (2011). We discover that L and s rise with age until ~3.2 Gyr and reduce rather rapidly afterward, while the optical maturity, OMAT, reduces monotonically with time. We show that in some situations, when not only OMAT but also L and s are incorporated in the estimation utilizing 750 & 950 nm photometry, the age estimation becomes considerably more reliable. We also observed that OMAT and the lunar cratering chronology function (cumulative number of craters larger than a certain diameter as a function of time) have a relatively linear relationship.

• Journal of Sensor Science and Technology
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• v.13 no.5
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• pp.399-404
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• 2004

We report on the technology of formation of sandwich structures based on fullerite films and on experimental results in research of optical and conductivity properties of these sandwich samples. Single crystals of sapphire (100) or silicon were used as substrates. The sandwich specimens were based on the structure M/$C_{60}$/M (M=Cr, Pd, Ag, Al, Cu). The thickness of the fullerite films was about $0.2{\sim}1.0{\mu}m$. The area of the $C_{60}$ film under the top contact was about $1cm^{2}$. The specimens have been investigated by infrared spectroscopy, spectra-photometry, ellipsometry and X-ray diffraction analysis. Measurements of the current/voltage characteristics and research on the temperature dependence of conductivity were performed as well. It was shown that metals such as Cr, Pd, Ag, Al, and Cu penetrate easily into the fullerite films. It appears that these specimens have a large conductivity. For silver/$C_{60}$ and other sandwich structures the conductivities show a semiconductor-like behaviour.