• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.585-587
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• 2008

Depending on host environments, $Eu^{2+}$ emission can be spectrally tuned by manipulating the energy levels between allowed $4f{\leftrightarrow}5d$ transition. Spectral variations of $Eu^{2+}$ emission from narrow green emission to broad yellow emission band were achieved by varying the host lattices such as Sr- or Ba-silicate, borate, and borosilicate.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.531-533
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• 2015

We have investigated the long term variability of the intensities of the broad-line region emission lines in the UV spectra of Seyfert I galaxy NGC 5548 from 1973-1996. We have obtained the following results: 1) a high level correlation between the intensities of emission lines as well as between intensities of emission lines and continuum fluxes was discovered. With increasing wavelength the correlation in both cases becomes weaker, 2) the relationship between the intensity of emission lines and the flux radiation in the continuum can be expressed by a power law function with coefficients of ${\alpha}{\approx}0.8-1.1$ for different lines. When the difference between the wavelengths of spectral lines and the continuum is increased, the value of the power function decreases, and 3) it was found that the magnitude of the variability of the line intensities are weaker than the range of variability of the continuum fluxes. The magnitude of the variability of the line intensities and the continuum fluxes increase at longer wavelengths.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.36.2-36.2
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• 2019

Fe II emission is a prominent and ubiquitous feature in the spectra of broad-line Active Galactic Nuclei (AGN) by producing a pseudo-continuum from UV to optical with complex and strong blends of the numerous emission lines themselves, other emission lines, and continuum. Since theoretical modeling of such intricate Fe II emission is very difficult and still far from able to reproduce observed data in detail, an empirical iron emission template, derived from observations of a narrow-line Seyfert 1 galaxy, is an essential and practical tool to obtain accurate measurements of all the emission lines and continuum in AGN spectra. However, the existing iron templates, based on the single prototypical strong Fe II emitter I Zw 1, are suffering from inadequate S/N and non-simultaneous, inconsistent data with limited wavelength coverage, which consequently limit the accuracy of all the spectral measurements. To overcome the limitations and construct an improved iron template with wide spectral coverage, high-quality UV and optical spectra for the new and better identified template galaxy, Mrk 493, were successfully obtained from our HST STIS program (GO-14744). We will show the preliminary results for multicomponent spectral decomposition of the data and template construction with application tests to various AGN spectra and comparison with previous templates.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.315-322
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• 2004

Several arguments have been presented in the literature to support the connection between radio halos and cluster mergers. The spectral index distributions of the halos in A665 and A2163 provide a new strong confirmation of this connection, i.e. of the fact that the cluster merger plays an important role in the energy supply to the radio halos. Features of the spectral index (flattening and patches) are indication of a complex shape of the radiating electron spectrum, and are therefore in support of electron reacceleration models. Regions of flatter spectrum are found to be related to the recent merger. In the undisturbed cluster regions, instead, the spectrum steepens with the distance from the cluster center. The plot of the integrated spectral index of a sample of halos versus the cluster temperature indicates that clusters at higher temperature tend to host halos with flatter spectra. This correlation provides further evidence of the connection between radio emission and cluster mergers.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.52.1-52.1
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• 2016

The Gamma-Ray Bursts (GRBs) are classified into the long GRBs (LGRBs) and the short GRBs (SGRBs). Their progenitors are expected to be different because they have its own distinct characteristics. Occasionally, the SGRBs having faint extended emission (EGRBs) are observed. The EGRBs exhibit the analogous properties that the SGRBs have, but observed T90 of the EGRBs is longer than two seconds as the LGRBs. Because the EGRBs have characteristics of the LGRBs and the SGRBs, study of the EGRBs is important to understand origins of the GRBs. In this study, we obtain the luminosity relations of the EGRBs observed by Swift/BAT. We compare these results with luminosity relations on the LGRBs and SGRBs. In addition, we examine the spectral lag relations of spike and extended emission component of the EGRBs detected by CGRO/BATSE, Konus/WIND, Swift/BAT, Fermi/GBM and compare to each other. We find that the luminosity relations of the EGRBs present different results with the LGRBs and the SGRBs. In the spectral lag relations, extended emission component expresses opposite results compared with spike component. Furthermore, the spectral lag relations from the four instruments came up with different outcomes to each other.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.263-268
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• 2008

The measurement of magnetic field is performed AC magnetic field emission density in driver cab and saloon's compartment of rolling stock. In order to measure magnetic-field emission, a three-axial magnetic-field sensor is used and connected to data process system. The AC magnetic field is checked and analysis through BNC output, DAQ cad and notebook PC. The spectral analysis is performed by short time Fourier transform(STFT) for time-domain emission signal.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.535-537
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• 2015

Interpreting ultraviolet-to-infrared (UV-to-IR) observations of galaxies in terms of constraints on physical parameters-such as stellar mass ($M_{\ast}$) and star formation rate (SFR)-requires spectral synthesis modelling. We investigate how increasing the level of sophistication of the standard simplifying assumptions of such models can improve estimates of galaxy physical parameters. To achieve this, we compile a sample of 1048 galaxies at redshifts 0.7 < z < 2.8 with accurate photometry at rest-frame UV to near-IR wavelengths from the 3D-HST Survey. We compare the spectral energy distributions of these galaxies with those from different model spectral libraries to derive estimates of the physical parameters. We find that spectral libraries including sophisticated descriptions of galaxy star formation histories (SFHs) and prescriptions for attenuation by dust and nebular emission provide a much better representation of the observations than 'classical' spectral libraries, in which galaxy SFHs are assumed to be exponentially declining functions of time, associated with a simple prescription for dust attenuation free of nebular emission. As a result, for the galaxies in our sample, $M_{\ast}$ derived using classical spectral libraries tends to be systematically overestimated and SFRs systematically underestimated relative to the values derived adopting a more realistic spectral library. We conclude that the sophisticated approach considered here is required to reliably interpret fundamental diagnostics of galaxy evolution.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.88.2-88.2
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• 2011

The far-ultraviolet (FUV) continuum and spectral images of C IV and H2 emission lines for the region of Orion-Eridanus Superbubble (OES) are hereby presented and compared with the maps obtained in other wavelengths. While the region shows complex structures, consisting of hot gases and cold dust, a close examination reveals that the FUV emission in this region can be understood reasonably as the result of their interactions. We confirm the origin of most diffuse FUV continuum to be starlight scattered by dust, but we also find that the ionized gas also contributes 50-70% of the total FUV intensity in the regions of H_alpha arcs. We note the bright diffuse FUV continuum in the eastern part of the northern dust-rich region, and attribute it to the bright early-type stars more abundant in this region than in the west as the amount of dust itself does not seem to be much different across 'arc A' that separates the two regions. In addition, two P Cygni-type stars are identified in this eastern region and their peculiar spectral profiles around the C IV emission line are anifested in the scattered diffuse spectrum. Besides this, the C IV emission is generally enhanced at the boundaries of the hot X-ray cavities where thin dust regions are located, confirming the thermal interface nature of the origin of this cooling emission line. The morphology of the H2 emission shows a general correlation with dust extinction features but its intensity peaks are rather located in thin dust areas, off the peak dust regions. Furthermore, H2 emission is seen to be weak in the arc A region though the arc passes through the center of the dust-rich area. Hence, the H2 emission and dust features, together with those of X-ray and ion lines emissions, show stratified structure of arc A quite well, again confirming its thermal interface nature.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.69-72
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• 2005

The FIMS (Far-ultraviolet IMaging Spectrograph; also known as SPEAR, Spectroscopy of Plasma Evolution from Astrophysical Radiation) is the primary payload of the STSAT-1, the first Korean science satellite, which was launched in September, 2003. The FIMS performs spectral imaging of diffuse far-ultraviolet emission with the unprecedented wide field of view and the relatively good spectral resolution. We present far-ultraviolet spectral observations of highly ionized interstellar medium including supernova remnants, superbubbles, soft X-ray shadows, and the molecular hydrogen fluorescent emission lines. The FIMS has detected He II, C III, 0 III, O IV, Si IV, O VI, and $H_2$ fluorescent emission lines. The emission lines arise in shocked or thermally heated and in photo-ionized gases. We present an overview of the FIMS instrument and its initial observational results.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.36.1-36.1
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• 2015

We present $5-14{\mu}m$ Infrared Spectrograph spectra of 14 T Tauri stars which show Polycyclic Aromatic Hydrocarbon (PAH) features and reside in 0.7 pc from ${\Theta}_1$ Ori C. The spectral types of nine out of 11 stars have spectral type information, with types ranging from K7-M5. These stars do not supply strong enough UV photons to excite PAH emission in their disks. Therefore, we consider the detection of PAH emission in disks around low mass stars illuminated by an external source of UV photons, namely, from Trapezium OB association, including ${\Theta}_1$ Ori C. The morphological features of PAH emission from most disks around K-M type host stars are unique, not belonging to any known classes of PAH features. We found that the PAH emission strengths decrease as the projected distance of the objects from ${\Theta}_1$ Ori C increase. We suggest future far-IR and submm/mm observations for better understanding of the characteristics and distribution of PAHs in these disks.