• 천문학회보
• /
• 제30권1호
• /
• pp.33.1-33.1
• /
• 2005

• 천문학회보
• /
• 제27권1호
• /
• pp.54-54
• /
• 2002

• 천문학회보
• /
• 제34권1호
• /
• pp.172.2-172.2
• /
• 2009

• 천문학회보
• /
• 제34권1호
• /
• pp.121-121
• /
• 2009

• 천문학회보
• /
• 제36권2호
• /
• pp.131.1-131.1
• /
• 2011

We present applications of clustering methods to detect variability in massive astronomical time series data. Focusing on variability of bright stars, we use clustering methods to separate possible variable sources from other time series data, which include intrinsically non-variable sources and data with common systematic patterns. We already finished the analysis of the Northern Sky Variability Survey data, which include about 16 million light curves, and present candidate variable sources with their association to other data at different wavelengths. We also apply our clustering method to the light curves of bright objects in the SuperWASP Data Release 1. For the analysis of the SuperWASP data, we exploit a elastically configurable Cloud computing environments that the KISTI Supercomputing Center is deploying. Two quite different configurations are incorporated in our Cloud computing test bed. One system uses the Hadoop distributed processing with its distributed file system, using distributed processing with data locality condition. Another one adopts the Condor and the Lustre network file system. We present test results, considering performance of processing a large number of light curves, and finding clusters of variable and non-variable objects.

• 천문학회보
• /
• 제39권1호
• /
• pp.78.2-78.2
• /
• 2014

Many techniques for data analysis also based on gaussian noise assumption which is often valid in various situations. However, the sensitivity of gravitational wave searches are limited by their non-gaussian and non-stationary noise. We introduce various on-going efforts to overcome this limitation in Korean Gravitational Wave Group. First, artificial neural networks are applied to discriminate non-gaussian noise artefacts and gravitational-wave signals using auxiliary channels of a gravitational wave detector. Second, viability of applying Hilbert-Huang transform is investigated to deal with non-stationary data of gravitational wave detectors. We also report progress in acceleration of low-latency gravitational search using GPGPU.

• 천문학회보
• /
• 제37권2호
• /
• pp.106.2-106.2
• /
• 2012

A Jupiter-family comet, 17P/Holmes, underwent an outburst on 2007 October 23. Since there has been no more dramatic comet outburst than the 17P/Holmes event in the history of modern astronomical observations, active observations were made soon after the outburst. However, little is known about the activity before the outburst because of the accidental event. In addition, since the nucleus has been veiled by the thick dust cloud by the 2007 outburst, the physical status of the nucleus was unknown. In this presentation, we investigated the contrast between before and after the outburst through the imaging observations in both optical and mid-infrared wavelengths. We thus analyzed data taken by Akari infrared telescope, Subaru 8-m telescope, University of Hawaii 2.2-m telescope and Nishi-Harima Astronomical Observatory 2-m Nayuta telescope. As the result, we found that the nucleus was significantly activated through the outburst. The surface fractional active area was 0.3% in the pre-outburst data while 10% in the past-outburst data. We expect that 17P/Holmes shows strenuous activity in the next return in 2013-2014.

• 천문학논총
• /
• 제19권1호
• /
• pp.101-107
• /
• 2004

This paper describes the digital back-end system for getting the data to analyze the user observation mode by digitalize the analog data after receiving the space radio using the radio telescope, The received analog data will be digitalized by high-speed sampler with 1 Gsps for 4 channel frequency band of millimeter wave, and the digital data will be transported through the fiber-optic digital transmission system and WDM(wavelength division multiplex) to observation building, The wideband digital FIR(Finite Impulse Response) filters analyze the data for user observation mode to record the data in high-speed recorder with 1 Gbps. In this paper, we introduce the overall system configuration and features combined by various information and communication technology in radio astronomy briefly, which will be adopted by KVN(Korean VLBI Network).

• 천문학회보
• /
• 제40권2호
• /
• pp.41.2-41.2
• /
• 2015

We have performed deep wide-field CCD photometry of the young open cluster IC 1805 in the famous star forming region W4, and obtained photometric data for more than 91,000 stars in the field of IC 1805 based on observations with the 3.6m CFHT and the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The photometric data cover an area $43^{\prime}{\times}45^{\prime}$ which is far larger and far deeper than any other optical observations made for the cluster. In order to select the young stellar objects with mid-IR excess emission, we have performed mid-IR photometry of the cluster using the archival images obtained with the Spitzer Space Telescope IRAC and MIPS instruments. From a preliminary analysis of the data, we determined the reddening law ($R_V=3.02{\pm}0.05$), distance modulus ($V_0-M_V=11.9{\pm}0.2$), and the spatial distribution of members.

• 천문학논총
• /
• 제20권1호
• /
• pp.55-62
• /
• 2005

The First Generation Digitized Sky Survey (DSS-I) is a collection of digitized photographic atlases of the night sky taken from the Palomar Observatory (northen sky) and the Anglo-Australian Observatory (southern sky). DSS-I is widely used by the astronomical community for a number of applications including object cross-identification and astrometry. However, accessing and retrieving the actual images are nontrivial owing to the huge size (> 60 GB) of the dataset. To facilitate retrieval process of DSS-I data for the public, Korean Astronomical Data Center (KADC) developed a web application that provides not only data retrieval but also visualization functions. The web application consists of several modules developed using Java Applet, Jave Servlet, and JaveServer Pages (JSP) technologies. It allows users to retrieve images efficiently in various formats such as FITS, JPEG, GIF, and TIFF, and also offers an interactive visulization tool, ImgViewer, for displaying/analyzing FITS images. To use the web application, users require a Java-enabled web browser.