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        검색결과 12

        1.
        2022.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Using I-band images of 35 nearby (z < 0.1) type 1 active galactic nuclei (AGNs) obtained with Hubble Space Telescope, selected from the 70-month Swift-BAT X-ray source catalog, we investigate the photometric properties of the host galaxies. With a careful treatment of the point-spread function (PSF) model and imaging decomposition, we robustly measure the I-band brightness and the effective radius of bulges in our sample. Along with black hole (BH) mass estimates from single-epoch spectroscopic data, we present the relation between BH mass and I-band bulge luminosity (MBH–MI,bul relation) of our sample AGNs. We find that our sample lies offset from the MBH–MI,bul relation of inactive galaxies by 0.4 dex, i.e., at a given bulge luminosity, the BH mass of our sample is systematically smaller than that of inactive galaxies. We also demonstrate that the zero point offset in the MBH–MI,bul relation with respect to inactive galaxies is correlated with the Eddington ratio. Based on the Kormendy relation, we find that the mean surface brightness of ellipticals and classical bulges in our sample is comparable to that of normal galaxies, revealing that bulge brightness is not enhanced in our sample. As a result, we conclude that the deviation in the MBH–MI,bul relation from inactive galaxies is possibly because the scaling factor in the virial BH mass estimator depends on the Eddington ratio.
        5,700원
        6.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this work, we study the correlation between the photon index (Γ) of the X-ray spectrum and the 2-10 keV X-ray luminosity (LX) for black hole X-ray binaries (BHBs). The BHB sample is mainly from the quiescent, hard and intermediate states, with values of LX ranging from ~ 1030.5 to 1037.5 erg s-1. We nd that the photon index Γ is positively or negatively correlated with the X-ray luminosity LX, for LX above or below a critical value, ~ 1036.5 erg s-1. This result is consistent with previous works. Moreover, when LX ≤ ~ 1033 erg s-1, we found that the photon index is roughly independent of the X-ray luminosity. We interpret the above correlations in the framework of a coupled hot accretion flow - jet model. Besides, we also find that in the moderate-luminosity region, different sources may have different anti-correlation slopes, and we argue this diversity is caused by the different value of δ, which describes the fraction of turbulent dissipation that directly heats electrons.
        3,000원
        8.
        2012.09 KCI 등재 구독 인증기관·개인회원 무료
        We combine data from two all-sky surveys, the Swift/Burst Alert Telescope 22 Month Source Catalog and the AKARI Point Source Catalogue, in order to study the connection between the hard X-ray (> 10 keV) and infrared (IR) properties of local active galactic nuclei (AGN). We find two photometric diagnostics are useful for source classification: one is the X-ray luminosity vs. IR color diagram, in which type 1 radio-loud AGN are well isolated from other AGN. The second one uses the X-ray vs. IR color-color diagram as a redshift-independent indicator for identifying Compton-thick (CT) AGN. Importantly, CT AGN and starburst galaxies in composite systems can also be separated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new surveys such as with WISE and NuSTAR.
        11.
        1996.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The x-ray pulsar GX 1+4 was observed by us in four balloon- borne experiments carried out from Hyderabad, India during 1991-1995 period with a hard x-ray telescope. The x-ray telescope consists of two collimated large area xenon-filled proportional counters with an effective area of 2400 cm2, a field of view of 5°×5° and sensitive in the energy band of 20 - 100 keV. The pulsar was detected in bright state in two of the four experiments and x-ray pulsations with 120 second period were detected clearly. Pulsation period, rate of change of period with time, pulse fraction, pulse profile and energy spectra of the source were determined from these studies. During March 1995 observation, the x-ray pulse of GX 1+4 was found to be double-peaked compared to a single-peak pulse profile detected in December 1993. Details of these results are presented and their interpretation discussed in terms of the current accretion models of x-ray binaries.
        3,000원
        12.
        2010.09 KCI 등재 서비스 종료(열람 제한)
        엑스선 영상의 공간분해능은 영상획득 장치에 사용되는 광학소자의 성능에 의해 결정된다. 8.5keV에서 높은 공간분 해능 달성이 가능한 존 플레이트를 설계하였다. 방사광을 이용하는 대신 엑스선 튜브를 사용하는 영상시스템에서는 80nm의 공간분해능을 달성할 수 있음을 광선추적 기법을 이용하여 예측하였다. 전자빔 석판인쇄술을 이용하여 최외곽 폭 40nm를 갖는 존 플레이트가 제작하였다.