• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.64.1-64.1
• /
• 2014

We study the dust and star-formation characteristics of a nearby dwarf elliptical galaxy, NGC 855. With various archival data from ultraviolet to far-infrared, we build up the spectral energy distribution (SED) that can give us constraints on stellar populations, dust characteristics, star-formation history, etc. From GALEX and SDSS data, slightly de-centered bluer central core is confirmed, where star formation might take place. This regions is coincident with seemingly dis-integrated cores detected by Spitzer IRAC data and with bright Ha feature observed at ground-based telescope. The PACS and SPIRE data by Herschel Space Observatory show the dominant dust features at the center. Lastly, we propose necessary follow-up observations with ground-based telescopes to investigate spectral properties of NGC 855.

• Journal of Astronomy and Space Sciences
• /
• v.18 no.2
• /
• pp.145-152
• /
• 2001

For the research of solar EUV (extreme ultraviolet) radiation, we have designed a small-sifted engineering model of solar EUV telescope, which is suitable for a Korean satellite. The EUV sole. telescope was designed to observe the sun at $584.3AA$(He I) and $629.7AA$(OV) The optical system is an f/8 Ritchey-Chr rien, and the effective diameter and focal length are 80mm and 640mm, respectively. The He I and 0V filters are loaded in a filter wheel. In the detection part, the MCP (Microchannel Plate) type is Z-stack, and the channel-to-diameter radio is 40:1. MCP and CCD are connected by fiber optic taper. A commercial optical design software is used for the analysis of the optical system design.

• Journal of Astronomy and Space Sciences
• /
• v.19 no.4
• /
• pp.273-282
• /
• 2002

We describe some performance of the detector electronics system for the FIMS (Far-ultraviolet Imaging Spectrograph) mission. The FIMS mission to map the far ultraviolet sky uses MCP (micro-channel plate) detectors with a crossed delay line anode to record photon arrival events. FIMS has two MCP detectors, each with a ~25mm$\times$25mm active area. The unconventional anode design allows for the use of a single set of position encoding electronics for both detector fields. The centroid position of the charge cloud, generated by the photon-stimulated MCP, is determined by measuring the arrival times at both ends of the anode following amplification and external delay. The temporal response of the detector electronics system determines the readout's positional resolution for the charge centroid. High temporal resolution (<$35{\times}75$ps FWHM) and low power consumption (< 6W) were achieved for the FIMS detector electronics system.

• Publications of The Korean Astronomical Society
• /
• v.20 no.1 s.24
• /
• pp.135-141
• /
• 2005

The FIMS(Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean Science Technology SATellite, STSAT-1, has performed various astronomical observations, including the Cygnus Loop, Vela supernova remnants, LMC(Large Magellanic Cloud), since its launch on September 2003. It has been found that the attitude information provided by spacecraft bus system has the errors of more than about 10-15 arcmins due to the time offset problem and errors in attitude knowledge. We develop an algorithm for correction of position errors in FIMS data. The aspect for the FIMS data is determined by comparing the positions of observed bright stars with the Tycho-II and TD-1 catalogs. The position errors of the bright stars along the scanning (${\gamma}$) and spatial (${\delta}$) directions were considered as functions of ${\delta}$, ignoring errors in position angle. The corrected positions of the bright stars coincided very well to their Tycho-II and TD-I positions. The correction algorithm is essential for the FIMS data analysis, and is being used for the FIMS data analysis.

• Journal of Astronomy and Space Sciences
• /
• v.21 no.4
• /
• pp.399-416
• /
• 2004

The FIMS (Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean science satellite STSAT-1, has performed various observations since its launch on September 2003. It has been found that the attitude informations provided by spacecraft bus system have a time offset problem, and the problem has been extensively studied. After the time offset correction, boresight offsets between FIMS fields of view, of long and short wavelength bands, respectivley, and spacecraft attitude systems, which are mainly due to alignment error between the FIMS and spacecraft mechanical systems, were calculated through the observations of well known calibration targets. Monthly status and precision of the attitude information are also described. Correction methods for spatially variable exposure, intrinsic to FIMS data, are discussed. These results are essential to the FIMS data analysis, and will be used as references for subsequent studies on more accurate attitude corrections.

• Journal of the Korean earth science society
• /
• v.25 no.6
• /
• pp.495-501
• /
• 2004

Using numerous ground-based or space-based telescopes by many astronomers, AGN spectroscopic monitoring campaigns have been carried out over many years to study the variability of continua and emission lines. We investigate the SWP IUE spectra of a large aperture configuration for the Seyfert 1 galaxies NGC 4151 and NGC 5548. We estimate the BLR electron number densities and their variation from the line ratios of C III] 1909 to Si III] 1892. With the ratios of C IV 1550 to C III] 1909 which give us the information on the ionization parameter of BLR, we try to find the physical conditions of the BLR and activities of he super massive black hole surroundings. The BLR density variations scale as 4 and 8 for NGC 4151 and NGC 5548, respectively. Based on the BLR size and C III] line profiles, we found both black hole masses as about $10^7$ $M_{\odot}$.