• Journal of The Korean Astronomical Society
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• v.47 no.3
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• pp.115-122
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• 2014

The New Vacuum Solar Telescope (NVST) is a 1-meter vacuum solar telescope that aims to observe the fine structures of active regions on the Sun. The main tasks of the NVST are high resolution imaging and spectral observations, including the measurements of the solar magnetic field. The NVST has been collecting more than 20 million FITS files since it began routine observations in 2012 and produces maximum observational records of 120 thousand files in a day. Given the large amount of files, the effective archiving and retrieval of files becomes a critical and urgent problem. In this study, we implement a new data archiving system for the NVST based on the Fastbit Not Only Structured Query Language (NoSQL) database. Comparing to the relational database (i.e., MySQL; My Structured Query Language), the Fastbit database manifests distinctive advantages on indexing and querying performance. In a large scale database of 40 million records, the multi-field combined query response time of Fastbit database is about 15 times faster and fully meets the requirements of the NVST. Our slestudy brings a new idea for massive astronomical data archiving and would contribute to the design of data management systems for other astronomical telescopes.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.48.2-48.2
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• 2010

Korean-Japanese Planet Search Program has been carried out since 2005 to search for planets around intermediate-mass giant stars (1.5-5.0 solar masses) by an international collaboration between Korean and Japanese researchers. In this program, we have been carrying out a precise radial velocity survey of about 190 G-type giant stars (6.21.9 solar masses) giant stars. These results extend the planet mass distribution of massive intermediate-mass stars to higher and lower mass region, and may further constrain substellar system formation mechanisms. We report the recent results and current status of Korean-Japanese Planet Search Program.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.92.1-92.1
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• 2013

In this study, we examined chromospheric oscillation signatures in two solar active regions, a limb active region and a sunspot with a light bridge, observed by the Fast Imaging Solar Spectrograph (FISS) of the 1.6m New Solar Telescope (NST) at Big Bear Solar Observatory. The FISS is a slit spectrograph with a fast imaging capability and can observe the solar chromosphere in $H{\alpha}$ and Ca II $8542{\AA}$ bands simultaneously with high spectral resolutions. After dark and flat correction, we compensated for image rotation at the Coude focus and made image alignment. We estimated Doppler shifts over active regions using the bisector method and investigated the temporal and spatial fluctuations of Doppler shifts for some selected cases. And we obtain the power map by using the Lomb-Scargle periodogram technique to examine the oscillation power at different features. Finally, we will discuss our results and implications.

• Journal of The Korean Astronomical Society
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• v.49 no.4
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• pp.157-162
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• 2016

High resolution reconstruction technology is developed to help enhance the spatial resolution of observational images for ground-based solar telescopes, such as speckle masking. Near real-time reconstruction performance is achieved on a high performance cluster using the Message Passing Interface (MPI). However, much time is spent in reconstructing solar subimages in such a speckle reconstruction. We design and implement a novel parallel method for speckle masking reconstruction of solar subimage on a shared memory machine using the OpenMP. Real tests are performed to verify the correctness of our codes. We present the details of several parallel reconstruction steps. The parallel implementation between various modules shows a great speed increase as compared to single thread serial implementation, and a speedup of about 2.5 is achieved in one subimage reconstruction. The timing result for reconstructing one subimage with 256×256 pixels shows a clear advantage with greater number of threads. This novel parallel method can be valuable in real-time reconstruction of solar images, especially after porting to a high performance cluster.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.63.1-63.1
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• 2019

Solar system small bodies are unusual objects in astronomical survey data in that they are moving on the celestial sphere. In addition, even in a normal status, their magnitudes are changing over time, firstly because their relative positions with respect to the Sun and Earth are continually changing, secondly because they are rotating bodies with non-spherical shapes. Furthermore, some of them might exhibit unexpected activities, which could be caused by mass ejection or disintegration. Detections and observations of such activities are challenging due to their abrupt nature. Therefore, continuous monitoring observations of large number of Solar system small bodies are required to systematically obtain detailed/transient information about them. Since 2018/2019 winter, we have launched a new project using Korea Microlensing Telescope Network (KMTNet) for detecting such transient phenomena of Solar system objects. Our main goal is to monitor the magnitudes and detect sudden brightness changes. We also plan to discover interesting new objects, and monitor rotational brightness oscillations of asteroids. We intend to monitor the magnitudes of ~ 20,000 known Solar system small bodies per night, and acquire lightcurves of ~ 1,000 asteroids.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.78.2-78.2
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• 2021

We present high resolution spectroscopic observations of transverse magnetohydrodynamic (MHD) waves in mottles located near the solar disk center. Different from previous studies that used transversal displacements of the mottles in the imaging data, we investigated the line-of-sight (LOS) velocity oscillations of the mottles in the spectral data. The observations were carried out by using the Fast Imaging Solar Spectrograph of the 1.6 meter Goode Solar Telescope of Big Bear Solar Observatory. Utilizing the spectral data of the Hα and Ca II 8542 Å lines, we measure the LOS velocity of a quiet region including the mottles and rosettes that correspond to the footpoints of the mottles. Our major findings are as follows: (1) Alfvénic waves are pervasive in the mottles. (2) The dominant period of the waves is 2 to 4 minutes. (3) From the time-distance maps of the three-minute filtered LOS velocity constructed along the mottles, it is revealed that the transverse waves in the mottles are closely related to the longitudinal waves in the rosettes. Our findings support the notion that Alfvénic waves can be generated by mode conversion of the slow magnetoacoustic waves as was shown in sunspot regions by Chae et al. (2021).

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.35.1-35.1
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• 2017

We present the characteristics and the performance of the new CCD camera system, SNUCAM-II (Seoul National University CAMera system II) that was installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory Australia in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength from $0.3{\mu}m$ to $1.1{\mu}m$ with high sensitivity (QE at 90%). It is equipped with SDSS ugriz filters and 13 medium band width (50nm) filters. On LSGT, SNUCAM-II covers $15.7{\times}15.7arcmin$ FOV at pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag at $5{\sigma}$ with 180s exposure time. SNUCAM-II will enable us to study Spectral Energy Distributions (SEDs) of diverse objects from extragalactic sources to solar objects in the southern hemisphere for research and education activities.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.29.2-29.2
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• 2018

Korean Neutrino Observatory (KNO) aims to make important discoveries in particle physics and astronomy by building a gigantic neutrino telescope consisting of 260 kiloton water and 40,000 20 inch photomultiplier tubes. Using J-PARC neutrino beam, leptonic CP violation (CPV) could be discovered if the CP is maximally violated, and neutrino mass ordering is guaranteed to be determined with more than 6 sigma for any CPV value. As a neutrino telescope, solar and Supernova burst/relic neutrinos could be studied very precisely. Indirect dark matter search sensitivity is improved by 3 to 4 times than that of Super Kamiokande. There are several candidate sites in Korea and especially Mt. Bisul and Mt. Bohyun are very promising according to our site survey. In this talk, an overview of the KNO is presented.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.83.1-83.1
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• 2019

Identifying asteroid families, which are groups of asteroids with similar orbital properties, is important for understanding the formation and evolution of the solar system, and probing the origins of Near-Earth Objects (NEOs). Although asteroid taxonomy can be used to identify and refine asteroid families, there are numerous asteroids which are not taxonomically classified yet. Korea Microlensing Telescope Network (KMTNet) can be useful to investigate types of that asteroids, because the telescope can observe a number of asteroids at once by its large field of view. Using KMTNet data, we confirmed that the taxonomic classification of the asteroids is possible by plotting color-color diagram. There is a clear division between C-type and S-type, but ambiguous division between C-type and X-type. In the future, we will observe and classify asteroids which are not classified yet and utilize the data to identify and refine asteroid families.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.88.2-88.2
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• 2013

Exploration of the wave-mode identification and its propagating property in the solar pore is desirable to study the energy transfer in the solar atmosphere. The Fast Imaging Solar Spectrograph (FISS) installed at the New Solar Telescope (NST) is a unique system that can do imaging of H-alpha and Ca II 8542 band simultaneously, which is quite suitable for studying of dynamics of chromosphere. In this study, we inspect a relationship between the cross-sectional area and intensity of the pore at continuum (-0.4 nm) near the Ca II line. We find coherent oscillations of the area and intensity. They shows out-of-phase (~ 180 degree difference) in photosphere, which implies that the oscillation is fast sausage mode. We also investigate a relationship between LOS velocities above the pore obtained from the Ca II and the Ha line cores, and find no significant difference of the phase (~10 degree) between the formation heights of the lines in chromosphere.