간행물
천문학논총 KCI 등재 Publications of the Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 연3회
- ISSN 1225-1534 (Print)2287-6936 (Online)
- 수록기간 1984 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
Volume 30 Issue 2 (2015년 9월) 186건
141.
2015.09
구독 인증기관 무료, 개인회원 유료
Chin-Ping Hu, Ching-Ping Lin, Yi Chou, Ting-Chang Yang, Yi-Hao Su, Hung-En Hsieh, Po-Sheng Chuang, Nai-Hui Liao
LMC X-4 is an eclipsing high-mass X-ray binary exhibiting a superorbital modulation with a period of ~ 30.5 days. We present a detailed study of the variations of the superorbital modulation period with a time baseline of ~ 18 years. The period determined in the light curve collected by the Monitor of All-sky X-ray Image (MAXI) significantly deviates from that observed by the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). Using the data collected by RXTE/ASM, MAXI, and the Burst Alert Telescope (BAT) onboard Swift, we found a significant period derivative, _P = (2.08±0.12) X 10-5. Furthermore, the O{C residual shows complex short-term variations indicating that the superorbital modulation of LMC X-4 exhibits complicated unstable behaviors. In addition, we used archive data collected by the Proportional Counter Array (PCA) on RXTE to estimate the orbital and spin parameters. The detected pulse frequencies obtained in small time segments were fitted with a circular orbital Doppler shift model. In addition to orbital parameters and spin frequency for each observation, we found a spin frequency derivative of v = (6.482 ± 0.011) X 10-13 Hz · s-1. More precise orbital and spin parameters will be evaluated by the pulse arrival time delay technique in the future.
3,000원
142.
2015.09
구독 인증기관 무료, 개인회원 유료
The short time scale X-ray variability associated with the accretion disk around compact objects is complex and is vaguely understood. The study of the cross correlation function gives an insight into the energy dependent behavior of the variations and hence connected processes. Using high resolution RXTE data, we investigate the dynamical cross correlation function of an observation of a black hole source XTE J1550-564 in the steep power law state. The cross correlation between soft and hard X- ray energy bands revealed both correlated and anti-correlated delays (≤ ±15 s) on a correlation time scale of 50 s. It was noticed that the observed delays were similar to the delays between X-ray and optical/IR bands in other black hole and neutron star sources. We discuss the possible mechanisms/processes to explain the observed delays in the dynamical CCF.
3,000원
143.
2015.09
구독 인증기관·개인회원 무료
Standard thin disk theory predicts that an inner disk region dominated by radiation pressure is thermally unstable. However, this kind of instability isn't detected in the observations of X-ray binaries. In this work, we revisit this issue by investigating the stability of a thin disk with magnetically driven winds. It is found that the disk winds can help to make a thin disk stable by taking away most of the energy released in the disk, resulting in a much cooler disk. The disk can always be stable even for a very weak initial field strength βp,0 ≤ 400 when α = 0.05 and Bø = 10Bp are adopted.
144.
2015.09
구독 인증기관 무료, 개인회원 유료
Chin-Ping Hu, Yi Chou, Ting-Chang Yang, Yi-Hao Su, Hung-En Hsieh, Ching-Ping Lin, Po-Sheng Chuang, Nai-Hui Liao
The development of time-frequency analysis techniques allow astronomers to successfully deal with the non-stationary time series that originate from unstable physical mechanisms. We applied a recently developed time-frequency analysis method, the Hilbert-Huang transform (HHT), to two non-stationary phenomena: the superorbital modulation in the high-mass X-ray binary SMC X-1 and the quasi-periodic oscillation (QPO) of the AGN RE J1034+396. From the analysis of SMC X-1, we obtained a Hilbert spectrum that shows more detailed information in both the time and frequency domains. Then, a phase- resolved analysis of both the spectra and the orbital profiles was presented. From the spectral analysis, we noticed that the iron line production is dominated by different regions of this binary system in different superorbital phases. Furthermore, a pre-eclipse dip lying at orbital phase ~ 0.6 - 0.85 was discovered dur- ing the superorbital transition state. We further applied the HHT to analyze the QPO of RE J1034+396. From the Hilbert spectrum and the O - C analysis results, we suggest that it is better to divide the evolu- tion of the QPO into three epochs according to their different periodicities. The correlations between the QPO periods and corresponding uxes were also different in these three epochs. The change in periodicity and the relationships could be interpreted as the change in oscillation mode based on the diskoseismology model.
3,000원
145.
2015.09
구독 인증기관 무료, 개인회원 유료
The Antarctic high plateau offers exceptional conditions for infrared and terahertz astronomy, as well as for programs requiring long, uninterrupted periods for measurements made with high cadence and photometric precision (i.e. time domain astronomy). In this review we summarise the special conditions of the Antarctic plateau which facilitate these observing regimes. We also outline some high profile science programs in each that could be conducted most effectively from the Antarctic high plateau, involving the first light in the Universe, the life cycle of our Galaxy, and the equation of state for the Universe. Three high plateau sites are under particular consideration for furthering such scientific programs-Dome A, Dome F and Ridge A. We summarise the activity underway at each site, which includes the building of new stations and the construction of facilities for optical, infrared and terahertz astronomy, as well as the plans for their future development.
4,000원
146.
2015.09
구독 인증기관 무료, 개인회원 유료
This paper presents an overview of the large international projects in which the National Astronomical Observatory of Japan is involved, namely, the Subaru Telescope, Atacama Large Millimeter/submillimeter Array, and the Thirty Meter Telescope. The last section provides a brief historical view of the international collaboration in East Asia regions over the last 20 years.
3,000원
147.
2015.09
구독 인증기관 무료, 개인회원 유료
Takao Nakagawa, Hiroshi Shibai, Takashi Onaka, Hideo Matsuhara, Hidehiro Kaneda, Yasuhiro Kawakatsu, SPICA Team
We present the current status (as of August 2014) of SPICA (Space Infrared Telescope for Cosmology and Astrophysics), which is a mission optimized for mid- and far-infrared astronomy with a cryogenically cooled 3m-class telescope. SPICA is expected to achieve high spatial resolution and unprecedented sensitivity in the mid- and far-infrared, which will enable us to address a number of key problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets. We have carried out the "Risk Mitigation Phase" activity, in which key technologies essential to the realization of the mission have been extensively developed. Consequently, technical risks for the success of the mission have been significantly mitigated. Along with these technical activities, the international collaboration framework of SPICA has been revisited, which resulted in la arger contribution from ESA than that in the original plan. To enable the ESA participation under the new framework, a SPICA proposal to ESA is under consideration as a medium-class mission under the framework of the ESA Cosmic Vision. The target launch year of SPICA under the new framework is the mid-2020s.
3,000원
148.
2015.09
구독 인증기관 무료, 개인회원 유료
P.A.R. Ade, Y. Akiba, A.E. Anthony, K. Arnold, M. Atlas, D. Barron, D. Boettger, J. Borrill, S. Chapman, Y. Chinone, M. Dobbs, T. Elleflot, J. Errard, G. Fabbian, C. Feng, D. Flanigan, A. Gilbert, W. Grainger, N.W. Halverson, M. Hasegawa, K. Hattori, M. Hazumi, W.L. Holzapfel, Y. Hori, J. Howard, P. Hyland, Y. Inoue, G.C. Jaehnig, A.H. Jaffe, B. Keating, Z. Kermish, R. Keskitalo, T. Kisner, M. LeJeune, A.T. Lee, E.M. Leitch, E. Linder, M. Lungu, F. Matsuda, T. Matsumura, X. Meng, N.J. Miller, H. Morii, S. Moyerman, M.J. Myers, M.J. Myers, M. Navaroli, H. Nishino, A. Orlando, H. Paar, J. Peloton, D. Poletti, E. Quealy, G. Rebeiz, C.L. Reichardt, P.L. Richards, C. Ross, I. Schanning, D.E. Schenck, B.D. Sherwin, A. Shimizu, C. Shimmin, M. Shimon, P. Siritanasak, G. Smecher, H. Spieler, N. Stebor, B. Steinbach, R. Stompor, A. Suzuki, S.Takakura, T. Tomaru, B. Wilson, A. Yadav, O. Zahn
Polarbear is a ground-based experiment located in the Atacama desert of northern Chile. The experiment is designed to measure the Cosmic Microwave Background B-mode polarization at several arcminute resolution. The CMB B-mode polarization on degree angular scales is a unique signature of primordial gravitational waves from cosmic in ation and B-mode signal on sub-degree scales is induced by the gravitational lensing from large-scale structure. Science observations began in early 2012 with an array of 1,274 polarization sensitive antenna-couple Transition Edge Sensor (TES) bolometers at 150 GHz. We published the first CMB-only measurement of the B-mode polarization on sub-degree scales induced by gravitational lensing in December 2013 followed by the first measurement of the B-mode power spectrum on those scales in March 2014. In this proceedings, we review the physics of CMB B-modes and then describe the Polarbear experiment, observations, and recent results.
3,000원
149.
2015.09
구독 인증기관 무료, 개인회원 유료
In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).
3,000원
150.
2015.09
구독 인증기관 무료, 개인회원 유료
KaVA (KVN and VERA Array) is a new combined VLBI array composed of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). Here, we report the following two issues. (1) We review the initial results of imaging observations of M87 at 23 GHz following Niinuma et al. (2014). The KaVA images reveal extended out ows including complex substructures such as knots and limb-brightening, in agreement with previous VLBI observations. KaVA achieves a high dynamic range of ~1000, more than three times better than that achieved by VERA alone. (2) Based on subsequent observations and discussions led by the KaVA AGN SubWorking Group, we set monitoring observations of Sgr A* and M87 as our Key Science Project (hereafter KSP) because of the closeness and largeness of their central super-massive black holes. The main science goals of the KSP are (i) testing the magnetically- driven-jet paradigm by mapping velocity fields of the M87 jet, and (ii) obtaining tight constraints on physical properties of the radio emitting region in Sgr A*. Towards KSP, we show the first preliminary images of M87 at 23 GHz and Sgr A* at 43 GHz with the bandwidth of 256 MHz.
3,000원
151.
2015.09
구독 인증기관 무료, 개인회원 유료
The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the rst international VLBI array dedicated to high-frequency (23 GHz (K-band) and 43 GHz (Q-band)) observations in East Asia. To evaluate the imagine capability of KaVA, we performed imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M87 by KaVA at K-/Q-band. Our KaVA images reveal extended out ows with complex substructure such as knots and limb brightening, in agreement with previous observations by other VLBI facilities. Angular resolutions are better than 1.4 and 0.8 milliarcsecond (max) at K-/Q-band, respectively. KaVA achieves a high dynamic range of ~1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN out ows, at least comparable to the best existing radio interferometric arrays.
3,000원
152.
2015.09
구독 인증기관 무료, 개인회원 유료
Yoshiaki Hagiwara, Tao An, Taehyun Jung, Duk-Gyoo Roh, Ming Zhang, Longfei Hao, Kenta Fujisawa, Yoshinori Yonekura, Willem Baan, Jongsoo Kim, Hideyuki Kobayashi
VLBI experiments have been conducted by radio telescopes in the East Asia VLBI Network (EAVN) in which 14 telescopes in China, Japan, and Korea participated. One of the aims of the EAVN is to obtain higher angular resolution that is provided by the 6,000 km baseline between China and Japan and better sensitivity by adding large telescopes. Data were recorded at 1 a Gbps recording rate at all stations and processed on the Korea-Japan Joint VLBI Correlator (KJJVC) at the Korea-Japan Correlation Center (KJCC) after experiments. Fringes were obtained from these experiments conducted at 8 GHz and 22 GHz and post-correlation data analysis of the experiments is undergoing. The outcomes of these experiments open the possibility of conducting EAVN observations with global VLBI networks. In this presentation, the recent status of these experiments and future prospects are presented.
3,000원
153.
2015.09
구독 인증기관 무료, 개인회원 유료
Koichiro Sugiyama, Kenta Fujisawa, Kazuya Hachisuka, Yoshinori Yonekura, Kazuhito Motogi, Satoko Sawada-Satoh, Naoko Matsumoto, Yu Saito, Daiki Hirano, Kyonosuke Hayashi, Zhiqiang Shen, Mareki Honma, Tomoya Hirota, Yasuhiro Murata, Akihiro Doi, Kotaro Niinuma, Richard Dodson, Maria Rioja, Simon Ellingsen, Xi Chen, Kee-Tae Kim, Hideo Ogawa
We have initiated a Very Long Baseline Interferometer (VLBI) monitoring project of 36 methanol maser sources at 6.7 GHz using the Japanese VLBI Network (JVN) and East-Asian VLBI Network (EAVN), starting in August 2010. The purpose of this project is to systematically reveal 3-dimensional (3-D) kine- matics of rotating disks around forming high-mass protostars. As an initial result, we present proper mo- tion detections for two methanol maser sources showing an elliptical spatial morphology, G 002.53+00.19 and G 006.79-00.25, which could be the best candidates associated with the disk. The detected proper motions indicate a simple rotation in G 002.53+00.19 and rotation with expansion in G 006.79-00.25, respectively, on the basis of disk model fits with rotating and expanding components. The expanding motions might be caused by the magnetic-centrifugal wind on the disk.
3,000원
154.
2015.09
구독 인증기관·개인회원 무료
O. Kameya, M. Tsuboi, Y. Asaki, Y. Yonekura, Y. Miyamoto, H. Kaneko, M. Seta, N. Nakai, M. Miyoshi, H. Takaba, K. Wakamatsu, Y. Fukuzaki, T. Morimitsu, M. Sekido
We have been performing daily VLBI monitoring of the ux density of Sagittarius (Sgr) A* at 22 GHz from February 2013 to August 2014 using a sub-array of the Japanese VLBI Network (JVN). The purpose of this monitoring is to explore the ux density variability at daily time resolution for a period longer than one year with the G2 cloud approaching. The ux density of Sgr A* is basically stable during the observational period, though there are some small variations. The average and scattering range are consistent with the previously observed values. We have observed no strong are of Sgr A* although it is near the expected peri-center passing.
155.
2015.09
구독 인증기관 무료, 개인회원 유료
Compared with traditional analog system, the Chinese VLBI Data Acquisition System (CDAS) is a digital one with better bandpass and wider bandwidth which allow weaker sources to be detected and measured by VLBI techniques. After optimizing and verifying the performance of CDAS in wide bandwidth observing mode, we performed an experiment by observing 85 weak sources along the ecliptic with Chinese VLBI stations located at Shanghai, Kunming and Urumqi. The capability of CDAS has been demonstrated for the detection of weak sources with improved sensitivity.
3,000원
156.
2015.09
구독 인증기관 무료, 개인회원 유료
The Australia Telescope National Facility (ATNF) consists of the Parkes and Mopra radio telescopes, and the Australia Telescope Compact Array, with the first elements of the wide-field Australian Square Kilometer Array Path nder (ASKAP), currently being commissioned. The capabilities of these facilities are described.
3,000원
157.
2015.09
구독 인증기관 무료, 개인회원 유료
The Long Baseline Array is an array of radio telescopes using the technique of Very Long Baseline Interferometry to achieve milli-arcsecond-scale angular resolution. The core telescopes are located in Australia, with telescopes in New Zealand and South Africa also participating regularly. In this paper the capabilities of the Long Baseline Array are described, and examples of the science undertaken with the array are given.
3,000원
158.
2015.09
구독 인증기관·개인회원 무료
The activities of IRSF, a 1.4m infrared telescope operated under collaboration between Japan and South Africa, are presented brie y. The dedicated instrument, SIRIUS, which sits at the Cassegrain, has produced unique and prosperous science for 14 years. My talk involves; o concept of construction and operation, o publications and education, o the successive upgrading of the instrument, and o future plans.
159.
2015.09
구독 인증기관 무료, 개인회원 유료
Robert A. Wittenmyer, John Asher Johnson, Jason Wright, Nate McCrady, Jonathan Swift, Michael Bottom, Peter Plavchan, Reed Riddle, Philip S. Muirhead, Erich Herzig, Justin Myles, Cullen H. Blake, Jason Eastman, Thomas G. Beatty, Brian Lin, Ming Zhao, Paul Gardner, Emilio Falco, Stephen Criswell, Chantanelle Nava, Connor Robinson, Richard Hedrick, Kevin Ivarsen, Annie Hjelstrom, Jon de Vera, Andrew Szentgyorgyi
The Kepler mission has shown that small planets are extremely common. It is likely that nearly every star in the sky hosts at least one rocky planet. We just need to look hard enough - but this requires vast amounts of telescope time. MINERVA (MINiature Exoplanet Radial Velocity Array) is a dedicated exoplanet observatory with the primary goal of discovering rocky, Earth-like planets orbiting in the habitable zone of bright, nearby stars. The MINERVA team is a collaboration among UNSW Australia, Harvard-Smithsonian Center for Astrophysics, Penn State University, University of Montana, and the California Institute of Technology. The four-telescope MINERVA array will be sited at the F.L. Whipple Observatory on Mt Hopkins in Arizona, USA. Full science operations will begin in mid-2015 with all four telescopes and a stabilised spectrograph capable of high-precision Doppler velocity measurements. We will observe ~100 of the nearest, brightest, Sun-like stars every night for at least five years. Detailed simulations of the target list and survey strategy lead us to expect 154 new low-mass planets.
4,000원
160.
2015.09
구독 인증기관 무료, 개인회원 유료
Before analyzing the images taken with a Mosaic CCD imager, the images have to reach a state which can be used for further scienti c analysis. The transformation of raw images into calibrated images is called data reduction. Transforming HEavely Light into Images (THELI) is a nearly fully automated reduction pipeline software (Erben et al., 2005). This pipeline works on raw images to remove instrumental signatures, mask unwanted signals, and perform photometric and astrometric calibration. Finally THELI constructs a deep co-added mosaic image and a weight map. In this poster, THELI data reduction procedures will be reviewed and the reduction process for raw images of seven X-ray bright groups, extracted from GEMS groups (Osmond & Ponman, 2004) obtained by the Wide Field Imager (WFI) mounted on MPG/ESO telescope at La Silla in March 2006 will be discussed.
3,000원
