간행물
천문학회지 KCI 등재 SCOPUS Journal of The Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 반년간
- ISSN 1225-4614 (Print)2288-890X (Online)
- 수록기간 1968 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
제52권 제1호 (2019년 2월) 3건
1.
2019.02
구독 인증기관 무료, 개인회원 유료
We present the results of the spectral and temporal analysis of eight X-ray point sources in five nearby (distance < 20 Mpc) galaxies observed with Chandra. For spectral analysis, an absorbed powerlaw and an absorbed diskblackbody were used as empirical models. Six sources were found to be equally fitted by both the models while two sources were better fitted by the powerlaw model. Based on model parameters, we estimate the X-ray luminosity of these sources in the energy range 0.3 − 10.0 keV, to be of the order of ∼ 1039ergs s−1 except for one source (X-8) with LX > 1040ergs s−1. Five of these maybe classified as Ultraluminous X-ray sources (ULXs) with powerlaw photon index within the range, Γ ∼ 1.63−2.63 while the inner disk temperature, kT ∼ 0.68−1.93 keV, when fitted with the disk blackbody model. The black hole masses harboured by the X-ray point sources were estimated using the disk blackbody model to be in the stellar mass range, however, the black hole mass of one source (X-6) lies within the range 68.37M ≤ MBH ≤ 176.32M, which at the upper limit comes under the Intermediate mass black hole range. But if the emission is considered to be beamed by a factor ∼ 5, the black hole mass reduces to ∼ 75M. The timing analysis of these sources does not show the presence of any short term variations in the kiloseconds timescales.
4,000원
2.
2019.02
구독 인증기관 무료, 개인회원 유료
Myungshin Im, Changsu Choi, Sungyong Hwang, Gu Lim, Joonho Kim, Sophia Kim, Gregory S. H. Paek, Sang-Yun Lee, Sung-Chul Yoon, Hyunjin Jung, Hyun-Il Sung, Yeong-beom Jeon, Shuhrat Ehgamberdiev, Otabek Burhonov, Davron Milzaqulov, Omon Parmonov, Sang Gak Lee, Wonseok Kang, Taewoo Kim, Sun-gill Kwon, Soojong Pak, Tae-Geun Ji, Hye-In Lee, Woojin Park, Hojae Ahn, Seoyeon Byeon, Jimin Han, Coyne Gibson, J. Craig Wheeler, John Kuehne, Chris Johns-Krull, Jennifer Marshall, Minhee Hyun, Seong-Kook J. Lee, Yongjung Kim, Yongmin Yoon, Insu Paek, Suhyun Shin, Yoon Chan Taak, Juhyung Kang, Seoyeon Choi, Mankeun Jeong, Moo-Keon Jung, Hwara Kim, Jisu Kim, Dayae Lee, Bomi Park, Keunwoo Park, Seong A O
Intensive Monitoring Survey of Nearby Galaxies (IMSNG) is a high cadence observation program monitoring nearby galaxies with high probabilities of hosting supernovae (SNe). IMSNG aims to constrain the SN explosion mechanism by inferring sizes of SN progenitor systems through the detection of the shock-heated emission that lasts less than a few days after the SN explosion. To catch the signal, IMSNG utilizes a network of 0.5-m to 1-m class telescopes around the world and monitors the images of 60 nearby galaxies at distances D < 50 Mpc to a cadence as short as a few hours. The target galaxies are bright in near-ultraviolet (NUV) with MNUV < - 18.4 AB mag and have high probabilities of hosting SNe (0.06 SN yr-1 per galaxy). With this strategy, we expect to detect the early light curves of 3.4 SNe per year to a depth of R 19:5 mag, enabling us to detect the shock-heated emission from a progenitor star with a radius as small as 0.1 R . The accumulated data will be also useful for studying faint features around the target galaxies and other science projects. So far, 18 SNe have occurred in our target fi elds (16 in IMSNG galaxies) over 5 years, confi rming our SN rate estimate of 0.06 SN yr-1 per galaxy.
4,200원
3.
2019.02
구독 인증기관 무료, 개인회원 유료
Guang-Yao Zhao, Taehyun Jung, Bong Won Sohn, Motoki Kino, Mareki Honma, Richard Dodson, Mar´ıa Rioja, Seog-Tae Han, Katsunori Shibata, Do-Young Byun, Kazunori Akiyama, Juan-Carlos Algaba, Tao An, Xiaopeng Cheng, Ilje Cho, Yuzhu Cui, Kazuhiro Hada, Jeffrey A. Hodgson, Wu Jiang, Jee Won Lee, Jeong Ae Lee, Kotaro Niinuma, Jong-Ho Park, Hyunwook Ro, Satoko Sawada-Satoh, Zhi-Qiang Shen, Fumie Tazaki, Sascha Trippe, Kiyoaki Wajima, Yingkang Zhang
The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving mode is demonstrated to be promising for mm-VLBI observations. Recently, other Very long baseline interferometry (VLBI) facilities all over the globe start to implement compatible optics systems. Simultaneous dual/multi-frequency VLBI observations at mm wavelengths with international baselines are thus possible. In this paper, we present the results from the first successful simultaneous 22/43 GHz dualfrequency observation with KaVA(KVN and VERA array), including images and astrometric results. Our analysis shows that the newly implemented simultaneous receiving system has brought a significant extension of the coherence time of the 43 GHz visibility phases along the international baselines. The astrometric results obtained with KaVA are consistent with those obtained with the independent analysis of the KVN data. Our results thus confirm the good performance of the simultaneous receiving systems for the non-KVN stations. Future simultaneous observations with more global stations bring even higher sensitivity and micro-arcsecond level astrometric measurements of the targets.
4,000원
