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SEJONG OPEN CLUSTER SURVEY (SOS) - V. THE ACTIVE STAR FORMING REGION SH 2-255 - 257 世宗疏散星团巡天(sos) - v.活跃恒星形成区sh 2-255 - 257
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-11-02 DOI: 10.5303/JKAS.2015.48.6.343
B. Lim, H. Sung, H. Hur, Byeong-Cheol Lee, M. Bessell, J. Kim, K. Lee, Byeong-Gon Park, G. Jeong
There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (R V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Г = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M ⊙ ). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.
有许多观测证据表明,活跃的恒星形成正在Hii区域Sh 2-255 - 257中发生。为了研究恒星的形成过程,我们利用从光学波段到中红外波段的成像数据对该恒星形成区域(SFR)进行了光度研究。根据不同的选择标准,共有218个成员被确定。SFR至少有E(B−V) = 0.8等的变红,向区域的变红规律正常(R V = 3.1)。用零年龄主序拟合方法证实了SFR与太阳的距离为2.1±0.3 kpc。根据赫茨普龙-罗素图(HRD)和恒星演化模型的比较,确定的成员的年龄中位数估计约为1.3兆年岁。初始质量函数(IMF)由HRD和近红外(J, J−H)色星等图导出。IMF的斜率约为Г =−1.6±0.1,比Salpeter/Kroupa IMF略陡。这意味着低质量恒星的形成在SFR中占主导地位。所有已识别成员的质量总和提供了星团质量的下限(169M⊙)。我们还利用Robitaille等人的SED拟合工具对主序前恒星的光谱能量分布(SED)进行了分析,证实了基于SED拟合工具和HRD的两种不同方法得到的恒星质量和年龄存在显著差异。
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引用次数: 4
MEASURING THE CORE SHIFT EFFECT IN AGN JETS WITH THE EXTENDED KOREAN VLBI NETWORK 用扩展的韩国vlbi网络测量agn喷气机的核心转移效应
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-10-31 DOI: 10.5303/JKAS.2015.48.5.277
T. Jung, R. Dodson, Seog-Tae Han, M. Rioja, D. Byun, M. Honma, J. Stevens, P. Vicente, B. Sohn
We present our efforts for extending the simultaneous multi-frequency receiver system of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) to global baselines in order to measure the frequency-dependent position shifts in Active Galactic Nuclei (AGN) jets, the so called core shift effect, with an unprecedented accuracy (a few micro-arcseconds). Millimeter VLBI observations with simultaneous multi-frequency receiver systems, like those of the KVN, enable us to explore the innermost regions of AGN and high precision astrometry. Such a system is capable of locating the frequency dependent opacity changes accurately. We have conducted the feasibility test-observations with the interested partners by implementing the KVN-compatible systems. Here we describe the science case for measuring the core shift effect in the AGN jet and report progress and future plans on extending the simultaneous multi-frequency system to global baselines.
为了以前所未有的精度(几微弧秒)测量活动星系核(AGN)喷流中与频率相关的位置位移,即所谓的核心位移效应,我们提出了将韩国甚长基线干涉(VLBI)网络(KVN)的同步多频接收器系统扩展到全球基线的努力。像KVN这样的多频同步接收系统的毫米波VLBI观测,使我们能够探索AGN的最内部区域和高精度的天体测量。这种系统能够准确地定位频率相关的不透明度变化。我们已与有兴趣的合作伙伴一起实施与kvn兼容的系统,进行可行性测试-观察。在这里,我们描述了测量AGN喷气机核心位移效应的科学案例,并报告了将同步多频系统扩展到全球基线的进展和未来计划。
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引用次数: 9
A SEARCH FOR AGN INTRA-DAY VARIABILITY WITH KVN 用KVN寻找agn的日变异性
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-10-28 DOI: 10.5303/JKAS.2015.48.5.313
Taeseok Lee, S. Trippe, Junghwan Oh, D. Byun, B. Sohn, Sang-Sung Lee Snu Seoul, Kasi Daejeon
Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a “anti-correlated” mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to assess the levels of variability and the corresponding upper limits. We found upper limits on flux variability ranging from ∼1.6% to ∼7.6%. The upper limits on the derived brightness temperatures exceed the inverse Compton limit by three to six orders of magnitude. From our results, plus comparison with data obtained by the University of Michigan Radio Astronomy Observatory, we conclude that we have not detected source-intrinsic variability which would have to occur at sub-per cent levels.
活动星系核(AGN)在所有时间尺度上都以不规则的变化而闻名,小到一天内的变化,在几分钟到几小时内相对变化几个百分点。在如此短的时间尺度上,仍然存在一些未开发的领域,例如可能存在最短的活动特征时间尺度和AGN功率谱的高频端形状。我们介绍了用韩国VLBI网络(KVN)进行的AGN单碟快速光度测定的结果。观测以“反相关”模式进行,使用两个天线,总是至少有一个天线指向目标。这将导致不到三分钟的有效时间分辨率。我们使用了所有四个KVN频率,22、43、86和129 GHz,以跟踪频谱变化,如果有的话。在2012年5月至2013年4月期间,我们能够获得3C 111, 3C 454.3和BL Lacertae在22和43 GHz以及3C 279在86 GHz的高质量光曲线。我们进行了详细的统计分析,以评估变异性的水平和相应的上限。我们发现通量可变性的上限在~ 1.6%到~ 7.6%之间。导出的亮度温度的上限超过逆康普顿极限三到六个数量级。从我们的结果,再加上与密歇根大学射电天文台获得的数据的比较,我们得出结论,我们没有探测到源的内在变化,这种变化必须在低于百分之一的水平上发生。
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引用次数: 0
KVN MONITORING OBSERVATIONS TOWARD THE RECENT OUTBURST SYMBIOTIC STAR V407 CYGNI 最近爆发共生星天鹅座v407的KVN监测观测
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-10-26 DOI: 10.5303/JKAS.2015.48.5.267
Se-Hyung Cho, Jaeheon Kim, Y. Yun
Simultaneous time monitoring observations of H₂O and SiO maser lines were performed toward the D-type symbiotic binary system V407 Cyg with the Korean VLBI Network single dish radio telescope. These monitoring observations were carried out from March 2, 2010 (optical phase ∅ = 0.0), 8 days before the nova outburst on March 10, 2010 to June 5, 2014 ( = 2.13). Eight days before the nova outburst, we detected the SiO v = 1, 2, J = 1–0 maser lines which exhibited values of 0.51 K (~ 6.70 Jy) and 0.71 K ( 9.30 Jy), respectively, while after the outburst we could not detect them on April 2 (∅ = 0.04), May 5 ( = 0.09), May 8 (∅ = 0.09), or on June 5, 2010 ( ∅ = 0.13) within the upper limits of our KVN observations. After restarting our monitoring observations, we detected SiO v = 2, J = 1–0 masers starting on October 20, 2011 (∅ = 0.83) and detected SiO v = 1, J = 1–0 masers starting on December 22, 2011 (∅ = 0.92). These results provide clear evidence of the interaction between the shock from the nova outburst and the SiO maser regions of the Mira envelope. The peak emission of SiO v = 1, 2, J = 1–0 masers always occurred at blueshifted velocities with respect to the stellar velocity except for that of SiO v = 1 at one epoch. These phenomena may be related to the redistribution of SiO maser regions after the outburst. The peak velocity variations of SiO masers associated with stellar pulsation phases show an increasing blueshifted trend during our monitoring interval after the outburst.
利用韩国VLBI网络单碟射电望远镜对d型共生双星系统V407 Cyg进行了H₂O和SiO脉泽线同步监测观测。观测时间为2010年3月2日(光学相位∅= 0.0),即2010年3月10日新星爆发前8天至2014年6月5日(= 2.13)。新星爆发前8天,我们分别探测到SiO v = 1、2、J = 1 - 0脉泽线,其值分别为0.51 K (~ 6.70 Jy)和0.71 K (9.30 Jy),而爆发后的4月2日(∅= 0.04)、5月5日(∅= 0.09)、5月8日(∅= 0.09)和2010年6月5日(∅= 0.13)在KVN观测上限内均未探测到。重新开始监测观测后,我们于2011年10月20日开始检测到SiO v = 2, J = 1 - 0脉泽(∅= 0.83);于2011年12月22日开始检测到SiO v = 1, J = 1 - 0脉泽(∅= 0.92)。这些结果为新星爆发产生的激波与Mira包层的SiO脉泽区之间的相互作用提供了明确的证据。SiO v = 1, 2, J = 1 - 0脉泽的峰值发射总是发生在相对于恒星速度的蓝移速度处,除了SiO v = 1在一个epoch的峰值发射。这些现象可能与爆发后SiO脉泽区重新分布有关。在爆发后的监测期间,SiO脉泽的峰值速度随恒星脉动相位的变化呈增加的蓝移趋势。
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引用次数: 1
INTERFEROMETRIC MONITORING OF GAMMA–RAY BRIGHT ACTIVE GALACTIC NUCLEI II: FREQUENCY PHASE TRANSFER 伽马射线明亮活动星系核的干涉监测ii:频率相位转移
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-10-20 DOI: 10.5303/JKAS.2015.48.5.237
J. Algaba, Guangyao Zhao, Sang-Sung Lee, D. Byun, Sincheol Kang, Dae-Won Kim, Jae-Young Kim, Jeong-Sook Kim, Soon-Wook Kim, M. Kino, A. Miyazaki, Jongho Park, S. Trippe, K. Wajima
The Interferometric Monitoring of Gamma–ray Bright Active galactic nuclei (iMOGABA) program provides not only simultaneous multifrequency observations of bright gamma–ray detected active galactic nuclei (AGN), but also covers the highest Very Large Baseline Interferometry (VLBI) frequencies ever being systematically monitored, up to 129 GHz. However, observation and imaging of weak sources at the highest observed frequencies is very challenging. In the second paper in this series, we evaluate the viability of the frequency phase transfer technique to iMOGABA in order to obtain larger coherence time at the higher frequencies of this program (86 and 129 GHz) and image additional sources that were not detected using standard techniques. We find that this method is applicable to the iMOGABA program even under non–optimal weather conditions.
伽马射线明亮活动星系核的干涉监测(iMOGABA)计划不仅提供了对探测到的活动星系核(AGN)的明亮伽马射线的同时多频观测,而且还覆盖了有史以来系统监测的最高甚大基线干涉测量(VLBI)频率,最高可达129 GHz。然而,在最高观测频率下观测和成像弱源是非常具有挑战性的。在本系列的第二篇论文中,我们评估了频率相位转移技术对iMOGABA的可行性,以便在该程序的较高频率(86和129 GHz)下获得更大的相干时间,并成像使用标准技术无法检测到的附加源。我们发现,即使在非最佳天气条件下,该方法也适用于iMOGABA程序。
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引用次数: 19
LEE SANG GAK TELESCOPE (LSGT): A REMOTELY OPERATED ROBOTIC TELESCOPE FOR EDUCATION AND RESEARCH AT SEOUL NATIONAL UNIVERSITY 李相阁望远镜(lsgt):首尔大学的远程遥控机器人望远镜,用于教育和研究
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-10-12 DOI: 10.5303/JKAS.2015.48.4.207
M. Im, Changsu Choi, Kihyun Kim
We introduce the Lee Sang Gak Telescope (LSGT), a remotely operated, robotic 0.43-meter telescope. The telescope was installed at the Siding Spring Observatory, Australia, in 2014 October, to secure regular and exclusive access to the dark sky and excellent atmospheric conditions in the southern hemisphere from the Seoul National University (SNU) campus. Here, we describe the LSGT system and its performance, present example images from early observations, and discuss a future plan to upgrade the system. The use of the telescope includes (ⅰ) long-term monitoring observations of nearby galaxies, active galactic nuclei, and supernovae; (ⅱ) rapid follow-up observations of transients such as gamma-ray bursts and gravitational wave sources; and (ⅲ) observations for educational activities at SNU. Based on observations performed so far, we nd that the telescope is capable of providing images to a depth of R = 21:5 mag (point source detection) at 5-σ with 15 min total integration time under good observing conditions.
李相阁望远镜(LSGT)是远程操作的0.43米机器人望远镜。该望远镜于2014年10月安装在澳大利亚赛丁泉天文台,目的是确保从首尔大学校园定期观测南半球黑暗的天空和良好的大气条件。在这里,我们描述了LSGT系统及其性能,展示了来自早期观测的示例图像,并讨论了未来升级系统的计划。望远镜的用途包括:(1)对邻近星系、活动星系核和超新星的长期监测观测;(二)伽马暴、引力波源等瞬变天体的快速跟踪观测;(三)对首尔大学教育活动的观察。根据目前的观测结果,在良好的观测条件下,该望远镜能够在5-σ、15 min的总积分时间内提供R = 21:5等(点源探测)深度的图像。
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引用次数: 10
a Study of a Tidally Interacting BCD Pair: ESO 435-IG20 and ESO435-IG16 潮汐相互作用BCD对ESO 435-IG20和ESO435-IG16的研究
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-09-30 DOI: 10.5303/PKAS.2015.30.2.513
Jinhyub Kim, E. Sung, A. Chung, L. Staveley-Smith
We investigate Hi data for a pair of blue compact dwarf galaxies (BCDs), ESO 435-IG20 and ESO 435-IG16, obtained with the Australia Telescope Compact Array. The outer Hi disk is highly disturbed and asymmetric in both galaxies showing a gas tail and/or a broad/extended gas disk on only one side. Based on their low-density surroundings and small projected distance (<80 kpc) at a similar redshift, we conclude that tidal interaction between these two BCDs is responsible for the morphological and kinematical peculiarities in Hi. We also investigate their star formation rates using H and UV imaging data to probe their interaction history.
我们研究了一对蓝紧凑型矮星系(bcd) ESO 435-IG20和ESO 435-IG16的Hi数据,这些数据是由澳大利亚望远镜紧凑型阵列获得的。外围的Hi盘在两个星系中都受到高度干扰和不对称,仅在一侧显示出气体尾巴和/或宽/延伸的气体盘。基于它们的低密度环境和类似红移的小投影距离(<80 kpc),我们得出结论,这两个bcd之间的潮汐相互作用是造成Hi的形态和运动学特性的原因。我们还利用H和UV成像数据研究了它们的恒星形成率,以探测它们的相互作用历史。
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引用次数: 0
PRE-PROCESSING OF GALAXIES IN THE FILAMENTS AROUND THE VIRGO CLUSTER 室女座星系团周围细丝中的星系的预处理
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-09-30 DOI: 10.5303/PKAS.2015.30.2.495
H. Yoon, A. Chung, C. Sengupta, O. I. Wong, M. Bureau, S. Rey, J. Gorkom
Galaxies can be pre-processed" in the low-density outskirts by ambient medium in the laments or tidal interactions with other galaxies while falling into the cluster. In order to probe how early on and by which mechanisms galaxies can be aected before they enter high-density cluster environments, we are carrying out an atomic hydrogen (Hi) imaging study of a sample of galaxies selected from three lamentary structures around the Virgo cluster. Our sample consists of 14 late-type galaxies, which are potentially interacting with their surroundings. The Hi observations have been done using the Westerbork Synthesis Radio Telescope, the Giant Metrewave Radio Telescope, and the Jansky Very Large Array with column density sensitivity of 3-5 10 19 cm 2 in 3 per channel, which is low enough to detect faint Hi features in the outer disks of galaxies. In this work, we present the Hi data of two galaxies that were observed with GMRT. We examine the Hi morphology and kinematics to nd the evidence for gas-gas and/or tidal interactions, and discuss which mechanism(s) could be responsible for pre-processing in these cases.
当星系落入星团时,可以在低密度的外围通过周围介质与其他星系的感流或潮汐相互作用进行“预处理”。为了探索星系在进入高密度星团环境之前的早期和通过何种机制可以受到影响,我们正在对从室女座星团周围的三个感伤结构中选择的星系样本进行原子氢(Hi)成像研究。我们的样本由14个晚期星系组成,它们可能与周围环境相互作用。利用韦斯特博克综合射电望远镜、巨型米波射电望远镜和杨斯基超大阵列进行了Hi观测,每个通道的柱密度灵敏度为3-5 - 10 - 19 cm 2 / 3,这个灵敏度足够低,可以探测到星系外盘微弱的Hi特征。在这项工作中,我们提出了用GMRT观测到的两个星系的Hi数据。我们研究了Hi的形态和运动学,以找到气-气和/或潮汐相互作用的证据,并讨论了在这些情况下哪种机制可能负责预处理。
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引用次数: 2
ANALYSIS OF THE LUNAR ECLIPSE RECORDS FROM THE GORYEOSA 高丽书院月食记录分析
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-08-01 DOI: 10.5303/JKAS.2016.49.4.163
Ki-Won Lee, Byeong-Hee Mihn, Y. Ahn, Sang-Hyeon Ahn
In this paper, we study the lunar eclipse records in the Goryeosa (History of the Goryeo Dynasty), an official history book of the Goryeo dynasty (A.D. 918 – 1392). In the history book, a total of 228 lunar eclipse accounts are recorded, covering the period from 1009 to 1392. However, we find that two accounts are duplications and four accounts correspond to no known lunar eclipses around the dates. For the remaining lunar eclipses, we calculate the magnitude and the time of the eclipse at different phases using the DE406 ephemeris. Of the 222 lunar eclipse accounts, we find that the minimum penumbral magnitude was 0.5583. For eclipses which occurred after midnight, we find that some accounts were recorded on the day before the eclipse, like the astronomical records of the Joseonwangjosillok (Annals of the Joseon Dynasty), while others were on the day of the lunar eclipse. We also find that four accounts show a difference in the Julian dates between this study and that of Ahn et al., even though it is assumed that the Goryeo court did not change the dates in the accounts for lunar eclipses that occurred after midnight. With regard to the contents of the lunar eclipse accounts, we confirm that the accounts recorded as total eclipses are accurate, except for two accounts. However, both eclipses were very close to the total eclipse. We also confirm that all predicted lunar eclipses did occur, although one eclipse happened two days after the predicted date. In conclusion, we believe that this study is very helpful for investigating the lunar eclipse accounts of other periods in Korea, and furthermore, useful for verifying the calendar dates of the Goryeo dynasty.
本文研究了高丽王朝(公元918 - 1392年)官方史书《高丽史》中关于月食的记载。在史书中,共有228次月食记录,时间跨度从1009年到1392年。然而,我们发现两种说法是重复的,四种说法对应的是在这些日期前后没有已知的月食。对于其余的月食,我们使用DE406星历计算月食在不同阶段的星等和时间。在222次月食记录中,我们发现最小半影星等为0.5583。对于发生在午夜之后的日食,我们发现,像《朝鲜王实录》的天文记录一样,有些记录在日食前一天,而有些记录在月食当天。我们还发现,有四种说法表明,在这项研究和Ahn等人的研究中,儒略历日期存在差异,尽管人们假设高丽朝廷没有改变发生在午夜之后的月食的日期。关于月食记载的内容,我们确认,除了两个记载外,记录为月全食的记载是准确的。然而,两次日食都非常接近日全食。我们还证实,所有预测的月食确实发生了,尽管有一次月食发生在预测日期的两天后。总之,我们认为这项研究对调查韩国其他时期的月食记载非常有帮助,而且对核实高丽王朝的历法日期也很有用。
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引用次数: 6
AMPLITUDE CORRECTION FACTORS OF KOREAN VLBI NETWORK OBSERVATIONS 韩国vlbi网观测的幅值校正因子
IF 1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2015-07-13 DOI: 10.5303/JKAS.2015.48.5.229
Sang-Sung Lee, D. Byun, C. Oh, H. Kim, Jongsoo Kim, T. Jung, Se-jin Oh, D. Roh, Dong-Kyu Jung, J. Yeom
We report results of investigation of amplitude calibration for very long baseline interferome-try (VLBI) observations with Korean VLBI Network (KVN). Amplitude correction factors are estimated based on comparison of KVN observations at 22 GHz correlated by Daejeon hardware correlator and DiFX software correlator in Korea Astronomy and Space Science Institute (KASI) with Very Long Base-line Array (VLBA) observations at 22 GHz by DiFX software correlator in National Radio Astronomy Observatory (NRAO). We used the observations for compact radio sources, 3C 454.3, NRAO 512, OJ 287, BL Lac, 3C 279, 1633+382, and 1510−089, which are almost unresolved for baselines in a range of 350-477 km. Visibility data of the sources obtained with similar baselines at KVN and VLBA are se-lected, fringe-fitted, calibrated, and compared for their amplitudes. We find that visibility amplitudes of KVN observations should be corrected by factors of 1.10 and 1.35 when correlated by DiFX and Daejeon correlators, respectively. These correction factors are attributed to the combination of two steps of 2-bit quantization in KVN observing systems and characteristics of Daejeon correlator.
本文报道了利用韩国VLBI网络(KVN)对甚长基线干涉仪(VLBI)观测进行幅度校准的研究结果。利用韩国天文空间科学研究所(KASI)大田硬件相关器和DiFX软件相关器相关的22 GHz KVN观测数据与国家射电天文台(NRAO) DiFX软件相关器相关的22 GHz甚长基线阵列(VLBA)观测数据进行对比,估算了振幅校正因子。我们使用了紧凑射电源的观测数据,3C 454.3、NRAO 512、OJ 287、BL Lac、3C 279、1633+382和1510−089,在350-477 km的基线范围内几乎无法解决。在KVN和VLBA获得的具有相似基线的源的能见度数据经过选择、条纹拟合、校准并比较其幅度。利用DiFX和大田相关器进行相关时,KVN观测值的能见度振幅应分别以1.10和1.35因子进行校正。这些校正因子是由于KVN观测系统中2位量化两步的结合和大田相关器的特性所致。
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引用次数: 19
期刊
Journal of the Korean Astronomical Society
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