Korean VLBI Network (KVN)

Recent Papers using KVN

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  • 2020-12
    A Study on Ring Buffer for Efficiency of Mass Data Transmission in Unstable Network Environment
    Min-Gyu Song and Hyo-Ryoung Kim
    Title A Study on Ring Buffer for Efficiency of Mass Data Transmission in Unstable Network Environment
    Date 2020-12
    Publication Journal of the KIECS., Volume 15, No. 6, 1045pp (2020)
    Authors Min-Gyu Song and Hyo-Ryoung Kim
    Affiliation Korea Astronomy and Space Science Institute
    Abstract In this paper, we designed a TCP/IP based ring buffer system that can stably transfer bulk data streams in the unstable network environments. In the scheme we proposed, The observation data stream generated and output by each radio observatory's backend system as a UDP frame is stored as a UDP packet in a large capacity ring buffer via a socket buffer in the client system. Thereafter, for stable transmission to the remote destination, the packets are processed in TCP and transmitted to the socket buffer of server system in the correlation center, which packets are stored in a large capacity ring buffer if there is no problem with the packets. In case of errors such as loss, duplication, and out of order delivery, the packets are retransmitted through TCP flow control, and we guaranteed that the reliability of data arriving at the correlation center. When congestion avoidance occurs due to network performance instability, we also suggest that performance degradation can be minimized by applying parallel streams.
    Link
    Attache file 논문_2020내부_비SCI_2_KIECS_Vol.15 No.06_1045-1054 (1).pdf
  • 2020-12
    Multidrop Ethernet based IoT Architecture Design for VLBI System Control and Monitor
    Min-Gyu Song
    Title Multidrop Ethernet based IoT Architecture Design for VLBI System Control and Monitor
    Date 2020-12
    Publication Journal of the KIECS., Volume 15, No. 6, 1159 pp. (2020)
    Authors Min-Gyu Song
    Affiliation Korea Astronomy and Space Science Institute
    Abstract In the past, control and monitor of a large number of instruments is a specialized area, which requires an expensive dedicated module to implement. However, with the recent development of embedded technology, various products capable of performing M&C (Monitor and Control) have been released, and the scope of application is expanding. Accordingly, it is possible to more easily build a small M&C environment than before. In this paper, we discussed a method to replace the M&C of the VLBI system, which had to be implemented through a specialized hardware product, with an inexpensive general imbeded technology. Memory based data transmission, reception and storage is a technology that is already generalized not only in VLBI but also in the network field, and more effective M&C can be implemented when some items of Ethernet are optimized for the VLBI (Very Long Baseline Interferometer) system environment. In this paper, we discuss in depth the design and implementation for the multidrop based IoT architecture.
    Link
    Attache file 논문_2020내부_비SCI_3_KIECS_Vol.15 No.06_1159-1168 (1).pdf
  • 2020-10
    Interferometric Monitoring of Gamma-Ray Bright AGNs: OJ 287
    arXiv:2009.02084v1 [astro-ph.GA] 4 Sep 2020Draft version September 7, 2020Typeset using LATEXpreprint2style in AASTeX62Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287Jee Won Lee,1Sang-Sung Lee,1, 2Juan-Carlos Algaba,3Jeffrey Hodgson,1, 4Jae-Young Kim,5Jongho Park,6Motoki Kino,7, 8Dae-Won Kim,9Sincheol Kang,1, 2Sungmin Yoo,10Sang Hyun Kim,1, 2and Mark Gurwell11
    Title Interferometric Monitoring of Gamma-Ray Bright AGNs: OJ 287
    Date 2020-10
    Publication The Astrophysical Journal, Volume 902, Number 2, 104 pp. (2020)
    Authors arXiv:2009.02084v1 [astro-ph.GA] 4 Sep 2020Draft version September 7, 2020Typeset using LATEXpreprint2style in AASTeX62Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287Jee Won Lee,1Sang-Sung Lee,1, 2Juan-Carlos Algaba,3Jeffrey Hodgson,1, 4Jae-Young Kim,5Jongho Park,6Motoki Kino,7, 8Dae-Won Kim,9Sincheol Kang,1, 2Sungmin Yoo,10Sang Hyun Kim,1, 2and Mark Gurwell11
    Affiliation 1Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea;Correspondence to Jee Won Lee at jwlee78@kasi.re.kr2University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea3Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia4Department of Physics and Astronomy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul, South Korea5Max-Planck-Institut fr Radioastronomie, Auf dem Hgel 69, D-53121 Bonn, Germany6Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan7National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan8Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo192-0015, Japan9Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Korea10Department of astronomy and space science, Chungbuk National University, Cheongju, 28644, Republic of Korea11Center for Astrophysics | Harvard&Smithsonian, 60 Garden Street, Cambridge, MA 02138 USA
    Abstract We present the results of simultaneous multifrequency imaging observations at 22, 43, 86, and 129 GHz of OJ 287. We used the Korean Very Long Baseline Interferometry Network as part of the Interferometric Monitoring of Gamma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15 GHz OVRO and 225 GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated timescales of three flux enhancements were similar with timescales of ~50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225 GHz enhancements led the 15 GHz enhancements by a range of 7–30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86 GHz. We could reliably measure the turnover frequency, ${
    u }_{{
    m{c}}}$, of the core of the source in three epochs. This was measured to be in a range from 27 to 50 GHz and a flux density at the turnover frequency, ${S}_{{
    m{m}}}$, ranging from 3 to 6 Jy. The derived SSA magnetic fields, ${B}_{mathrm{SSA}}$, are in a range from 0.157 ± 0.104 to 0.255 ± 0.146 mG. We estimated the equipartition magnetic field strengths to be in a range from 0.95 ± 0.15 to 1.93 ± 0.30 mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of ${B}_{mathrm{SSA}}$. We conclude that the downstream jet may be more particle energy dominated.
    Link
    Attache file
  • 2020-10
    Searching for shocks in high-mass starless clump candidates
    Feng-Yao Zhu,1⋆Jun-Zhi Wang,1Tie Liu1,2Kee-Tae Kim2,3Qing-Feng Zhu4and Fei Li1
    Title Searching for shocks in high-mass starless clump candidates
    Date 2020-10
    Publication Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 4, 6018 pp. (2020)
    Authors Feng-Yao Zhu,1⋆Jun-Zhi Wang,1Tie Liu1,2Kee-Tae Kim2,3Qing-Feng Zhu4and Fei Li1
    Affiliation 1Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, 200030, China2Korea Astronomy and Space Science Institute, Daejeon, 34055, Korea3University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea4CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China,Hefei, 230026, China
    Abstract In order to search for shocks in the very early stage of star formation, we performed single-point surveys of SiO J = 1–0, 2–1, and 3–2 lines and the H2CO 212−111 line towards a sample of 100 high-mass starless clump candidates (SCCs) by using the Korean VLBI Network (KVN) 21-m radio telescopes. The detection rates of the SiO J = 1–0, 2–1, 3–2 lines, and the H2CO line are 31.0⁠, 31.0⁠, 19.5, and 93.0 per cent⁠, respectively. Shocks seem to be common in this stage of massive star formation. The widths of the observed SiO lines [full width at zero power (FWZP)] range from 3.4 to 55.1 km s−1. A significant fraction (⁠∼29 per cent⁠) of the detected SiO spectra have broad line widths (FWZP > 20 km s−1), which are very likely associated with fast shocks driven by protostellar outflows. This result suggests that about one third of the SiO-detected SCCs are not really starless but protostellar. On the other hand, about 40  per cent of the detected SiO spectra show narrow line widths (FWZP < 10 km s−1) probably associated with low-velocity shocks which are not necessarily protostellar in origin. The estimated SiO column densities are mostly 0.31−4.32 × 1012 cm−2. Comparing the SiO column densities derived from SiO J = 1–0 and 2–1 lines, we suggest that the SiO molecules in the SCCs may be in the non-LTE condition. The SiO abundances to H2 are usually 0.20−10.92 × 10−10.
    Link https://doi.org/10.1093/mnras/staa3100
    Attache file
  • 2020-09
    Precise radio astrometry and new developments for the next generation of instruments
    Mar ́ıa J. Rioja 1,2,3 and Richard Dodson 2
    Title Precise radio astrometry and new developments for the next generation of instruments
    Date 2020-09
    Publication Astron Astrophys Rev., Volume 28, 6 pp (2020)28
    Authors Mar ́ıa J. Rioja 1,2,3 and Richard Dodson 2
    Affiliation 1 CSIRO Astronomy and Space Science, 26 Dick Perry Avenue, Kensington, WA 6151, Australia
    2 International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, Australia
    3 Observatorio Astrono ́mico Nacional (IGN), Alfonso XII, 3 y 5, 28014 Madrid, Spain
    Abstract We present a technique-led review of the progression of precise radio astrometry, from the first demonstrations, half a century ago, until to date and into the future. We cover the developments that have been fundamental to allow high accuracy and precision astrometry to be regularly achieved. We review the opportunities provided by the next generation of instruments coming online, which are primarily: SKA, ngVLA, and pathfinders, along with EHT and other (sub)mm-wavelength arrays, Space-VLBI, Geodetic arrays, and optical astrometry from GAIA. From the his- torical development, we predict the future potential astrometric performance, and, therefore, the instrumental requirements that must be provided to deliver these. The next generation of methods will allow ultra-precise astrometry to be performed at a much wider range of frequencies (hundreds of MHz to hundreds of GHz). One of the key potentials is that astrometry will become generally applicable, and, there- fore, unbiased large surveys can be performed. The next-generation methods are fundamental in allowing this. We review the small but growing number of major astrometric surveys in the radio, to highlight the scientific impact that such projects can provide. Based on these perspectives, the future of radio astrometry is bright. We foresee a revolution coming from: ultra-high-precision radio astrometry, large surveys of many objects, improved sky coverage, and at new frequency bands other than those available today. These will enable the addressing of a host of innovative open scientific questions in astrophysics.
    Link https://doi.org/10.1007/s00159-020-00126-z(0123456789().,-vol(V0)123456789().,-volV)
    Attache file 논문_2020외부_1_0929_Rioja_Dodson__Precise radio astrometry.pdf
  • 2020-09
    Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed γ-Ray Blazar JVAS B0218+357
    Kazuhiro Hada1,2 , Kotaro Niinuma3 , Julian Sitarek4 , Cristiana Spingola5,6 , and Ayumi Hirano3
    Title Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed γ-Ray Blazar JVAS B0218+357
    Date 2020-09
    Publication The Astrophysical Journal, Volume 901, 2 pp. (2020)
    Authors Kazuhiro Hada1,2 , Kotaro Niinuma3 , Julian Sitarek4 , Cristiana Spingola5,6 , and Ayumi Hirano3
    Affiliation 1 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan; kazuhiro.hada@nao.ac.jp 2 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    3 Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yoshida 1677-1, Yamaguchi, Yamaguchi 753-8512, Japan
    4 University of Łódź, 90236 Łódź, Poland
    5 INAF−Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy
    6 Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy
    Abstract We observed the gravitationally lensed blazar JVASB0218+357 with the KVN and VERA Array (KaVA) at 22, 43, and 86 GHz. The source has recently been identified as an active γ-ray source up to GeV/TeV energy bands, rendering a unique target for studying relativistic jets through gravitational lensing. Here we report the first robust very long baseline interferometry (VLBI) detection and imaging of the lensed images up to 86 GHz. The detected milliarcsecond-scale/parsec-scale morphology of the individual lensed images (A and B) is consistent with that previously seen at 22 and 15 GHz, showing the core–jet morphology with the jet direction being the same as at the low frequencies. The radio spectral energy distributions of the lensed images become steeper at higher frequencies, indicating that the innermost jet regions become optically thin to synchrotron emission. Our findings confirm that the absorption effects due to the intervening lensing galaxy become negligible at millimeter wavelengths. These results indicate that high-frequency VLBI observations are a powerful tool to better recover the intrinsic properties of lensed active galactic nucleus jets, which therefore allow us to study the interplay between the low- and high- energy emission.
    Link https://doi.org/10.3847/1538-4357/abaab1
    Attache file 논문_2020외부_5_0920_Hada_2020_ApJ_901_2_Millimeter-VLBI Detection and Imaging.pdf
  • 2020-07
    Detection of Periodicity in SiO Maser Intensity and Velocity Shift of the Symbiotic Star CH Cyg
    Se-Hyung Cho1,2 , Haneul Yang2 , Youngjoo Yun2 , Dong-Hwan Yoon2, Jaeheon Kim3, and Dong-Jin Kim4
    Title Detection of Periodicity in SiO Maser Intensity and Velocity Shift of the Symbiotic Star CH Cyg
    Date 2020-07
    Publication The Astrophysical Journal Letters, Volume 897, L26 pp. (2020)
    Authors Se-Hyung Cho1,2 , Haneul Yang2 , Youngjoo Yun2 , Dong-Hwan Yoon2, Jaeheon Kim3, and Dong-Jin Kim4
    Affiliation 1 Astronomy program, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea; cho@kasi.re.kr
    2 Korea Astronomy and Space Science Institute, Yuseong–gu, Daejeon 34055, Republic of Korea
    3 Department of Astronomy and Space Science, Chungbuk National University, Cheongju 28644, Republic of Korea
    4 Max-Planck-Institut fu ̇r Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
    Abstract We performed simultaneous monitoring observations of H2O 616–523 and SiO v=1, 2, J = 1 0, SiO v=1, J = 2 1, 3  2 maser lines toward the symbiotic star CH Cyg from 2012 December to 2019 November using the Korean very long baseline interferometry Network single-dish telescope. SiO v=1, 2, J = 1  0 and v=1, J = 2  1 maser lines were detected for the first time. A periodicity of about 2.5 yr in the SiO maser intensity was found, showing its association with the pulsation of the M giant in CH Cyg. Only the SiO v=2, J = 1  0 maser, without detections of the v=1, J = 1  0 maser, was detected in 6 epochs out of 15 v=2, J=1–0 maser detected epochs. In addition, the SiO v=1, J = 2  1 maser intensity was always stronger than that of the v=1, J = 1  0 maser except for one epoch, providing a critical constraint on the different masing conditions by different transitions, according to changes of the CH Cyg symbiotic system. We also found the gradual redshifted peak velocities of the SiO masers had about a 2.5 yr periodicity corresponding to the period of peak intensities (redshifted up to about +40 km s-1 with respect to the stellar velocity of the M giant). Two possible explanations can be suggested for the 2.5 yr period of the SiO maser intensity and velocity behaviors, although their actual causes remain uncertain.
    Link https://iopscience.iop.org/article/10.3847/2041-8213/ab9f99
    Attache file 200710_Cho_2020_ApJL_897_L26.pdf
  • 2020-06
    Multiple Outflows in the High-mass Cluster-forming Region G25.82–0.17
    Jungha Kim1,2 , Mi Kyoung Kim3,4 , Tomoya Hirota1,2 , Kee-Tae Kim5,6 , Koichiro Sugiyama2,7 , Mareki Honma1,3 , Do-young Byun5,6 , Chungsik Oh5, Kazuhito Motogi8, Jihyun Kang5 , Jeongsook Kim5, Tie Liu9 , Bo Hu10 ,
    Ross A. Burns2,5 , James O. Chibueze11,12 , Naoko Matsumoto2,13, and Kazuyoshi Sunada3
    Title Multiple Outflows in the High-mass Cluster-forming Region G25.82–0.17
    Date 2020-06
    Publication The Astrophysical Journal, Volume 896, 127 pp. (2020)
    Authors Jungha Kim1,2 , Mi Kyoung Kim3,4 , Tomoya Hirota1,2 , Kee-Tae Kim5,6 , Koichiro Sugiyama2,7 , Mareki Honma1,3 , Do-young Byun5,6 , Chungsik Oh5, Kazuhito Motogi8, Jihyun Kang5 , Jeongsook Kim5, Tie Liu9 , Bo Hu10 ,
    Ross A. Burns2,5 , James O. Chibueze11,12 , Naoko Matsumoto2,13, and Kazuyoshi Sunada3
    Affiliation 1 Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21 Hoshi-ga-oka, Mizusawa-ku, Oshu, Iwate 023-0861, Japan
    4 Department of Child Studies, Faculty of Home Economics, Otsuma Women’s University, 12 Sanban-cho, Chiyoda-ku, Tokyo 102-8357, Japan
    5 Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 34055, Republic of Korea
    6 University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
    7 National Astronomical Research Institute of Thailand (Public Organization), 260 Moo 4, T. Donkaew, A. Maerim, Chiang Mai 50180, Thailand
    8 Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512, Japan
    9 Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China
    10 School of Astronomy and Space Science, Nanjing University, 22 Hankou Road, Nanjing 210093, People’s Republic of China
    11 Space Research Unit, Physics Department, North West University, Potchefstroom 2520, South Africa
    12 Department of Physics and Astronomy, Faculty of Physical Sciences, University of Nigeria, Carver Building, 1 University Road, Nsukka, Nigeria
    13 The Research Institute for Time Studies, Yamaguchi University, Yoshida 167701, Yamaguchi, Yamaguchi 753-8511, Japan
    Abstract We present results of continuum and spectral line observations with Atacama Large Millimeter/submillimeter Array (ALMA) and 22 GHz water (H2O) maser observations using the KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry) array (KaVA) toward a high-mass star-forming region, G25.82–0.17. Multiple 1.3 mm continuum sources are revealed, indicating the presence of young stellar objects (YSOs) at different evolutionary stages, namely an ultracompact H II region, G25.82–E, a high-mass young stellar object (HM-YSO), G25.82–W1, and starless cores, G25.82–W2 and G25.82–W3. Two SiO outflows, at N–S and SE– NW orientations, are identified. The CH3OH 8−1–70 E line, known to be a Class I CH3OH maser at 229 GHz, is also detected, showing a mixture of thermal and maser emission. Moreover, the H2O masers are distributed in a region ∼0 25 shifted from G25.82–W1. The CH3OH 224–215 E line shows a compact ringlike structure at the position of G25.82–W1 with a velocity gradient, indicating a rotating disk or envelope. Assuming Keplerian rotation, the dynamical mass of G25.82–W1 is estimated to be >25 Me and the total mass of 20–84 Me is derived from the 1.3 mm continuum emission. The driving source of the N–S SiO outflow is G25.82–W1 while that of the SE–NW SiO outflow is uncertain. Detection of multiple high-mass starless/protostellar cores and candidates without low-mass cores implies that HM-YSOs could form in individual high-mass cores as predicted by the turbulent core accretion model. If this is the case, the high-mass star formation process in G25.82 would be consistent with a scaled-up version of low-mass star formation.
    Link https://iopscience.iop.org/article/10.3847/1538-4357/ab9100
    Attache file 200620_JHKim_2020_ApJ_896_127.pdf
  • 2020-06
    FLASHING: New high-velocity H2O masers in IRAS 18286−0959
    Hiroshi IMAI ,1,2,3,∗ Yuri UNO,3 Daichi MAEYAMA,4 Ryosuke YAMAGUCHI,4 KeiAMADA,3YuhkiHAMAE,4GaborOROSZ,5,6Jose ́F.GO ́MEZ,7 Daniel TAFOYA,8,9 Lucero USCANGA,10 and Ross A. BURNS 8,11
    Title FLASHING: New high-velocity H2O masers in IRAS 18286−0959
    Date 2020-06
    Publication ubl. Astron. Soc. Japan, Volume 72, No. 4, 58 pp (2020)
    Authors Hiroshi IMAI ,1,2,3,∗ Yuri UNO,3 Daichi MAEYAMA,4 Ryosuke YAMAGUCHI,4 KeiAMADA,3YuhkiHAMAE,4GaborOROSZ,5,6Jose ́F.GO ́MEZ,7 Daniel TAFOYA,8,9 Lucero USCANGA,10 and Ross A. BURNS 8,11
    Affiliation 1Amanogawa Galaxy Astronomy Research Center, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
    2Center for General Education, Institute for Comprehensive Education, Kagoshima University, 1-21-30 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
    3Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
    4Department of Physics and Astronomy, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
    5School of Natural Sciences, University of Tasmania, Private Bag 37, Hobart, Tasmania 7001, Australia 6Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi,
    Xinjiang 830011, China
    7Instituto de Astrof ́ısica de Andaluc ́ıa, CSIC, Glorieta de la Astronom ́ıa s/n, E-18008 Granada, Spain 8National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan 9Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space
    Observatory, 439 92 Onsala, Sweden
    10Departamento de Astronom ́ıa, Universidad de Guanajuato, A.P. 144, 36000 Guanajuato, Gto., Mexico 11Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055,
    Republic of Korea
    Abstract We discovered new high-velocity components of H2O maser emission in one of the “water fountain” sources, IRAS 18286−0959, which has been monitored using the Nobeyama 45 m telescope in the FLASHING (Finest Legacy Acquisitions of SiO- and H2 O-maser Igni- tions by Nobeyama Generation) project since 2018 December. The maser spectra show new components with extremely high expansion velocities (>200 km s−1 projected in the line of sight), some of which are located symmetrically in the spectrum with respect to the systemic velocity. They were also mapped with KaVA (KVN and VERA Combined Array) in 2019 March. We located some of these maser components closer to the cen- tral stellar system than other high-velocity components (50–200 km s−1 ) that have been confirmed to be associated with the known bipolar outflow. The new components would have flashed in the fast collimated jet at a speed of over 300 km s−1 (soon) after 2011 when they had not been detected. The fastest of the new components seem to indicate rapid deceleration in these spectra; however, our present monitoring is still too sparse o unambiguously confirm it (up to 50 km s−1 yr−1 ) and too short to reveal their terminal expansion velocity, which will be equal to the expansion velocity that has been observed (vexp ∼ 120 km s−1). Future occurrences of such extreme-velocity components may pro- vide a good opportunity to investigate possible recurrent outflow ignitions. Thus, the sculpture of the parental envelope will be traced by the dense gas that is entrained by the fast jet and exhibits spectacular distributions of the relatively stable maser features.
    Link doi: 10.1093/pasj/psaa047
    Attache file 논문_2020외부_3_0605_psaa047_FLASHING-New high-velocity.pdf
  • 2020-05
    Constraints on the Circumnuclear Disk through Free–Free Absorption in the Nucleus of 3C 84 with KaVA and KVN at 43 and 86 GHz
    Kiyoaki Wajima1 , Motoki Kino2,3 , and Nozomu Kawakatu4
    Title Constraints on the Circumnuclear Disk through Free–Free Absorption in the Nucleus of 3C 84 with KaVA and KVN at 43 and 86 GHz
    Date 2020-05
    Publication The Astrophysical Journal Letters, Volume 866, 35 pp. (2020)
    Authors Kiyoaki Wajima1 , Motoki Kino2,3 , and Nozomu Kawakatu4
    Affiliation 1 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong, Daejeon 34055, Republic of Korea; wajima@kasi.re.kr
    2 Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan 3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    4 National Institute of Technology, Kure College, 2-2-11 Agaminami, Kure, Hiroshima 737-8506, Japan
    Abstract The nearby bright radio galaxy 3C84 at the center of the Perseus cluster is an ideal target to explore the jet in an active galactic nucleus and its parsec-scale environment. The recent research of Fujita & Nagai revealed the existence of the northern counter-jet component (N1) located 2mas north from the central core in very long baseline interferometer (VLBI) images at 15 and 43GHz and they are explained by the free–free absorption (FFA) due to an ionized plasma foreground. Here we report a new quasi-simultaneous observation of 3C84 with the Korean VLBI Network (KVN) at 86GHz and the KVN and VLBI Exploration of Radio Astrometry Array (KaVA) at 43GHz in 2016 February. We succeeded the first detection of N1 at 86GHz and the data show that N1 still has an inverted spectrum between 43 and 86GHz with its spectral index α (Sn μ na) of 1.19±0.43, while the approaching lobe component has a steep spectrum with an index of −0.54±0.30. Based on the measured flux asymmetry between the counter and approaching lobes, we constrain the averaged number density of the FFA foreground ne as 1.8 ́ 104 cm-3  ne  1.0 ́ 106 cm-3. Those results suggest that the observational properties of the FFA foreground can be explained by the dense ionized gas in the circumnuclear disk and/or assembly of clumpy clouds at the central ∼1pc region of 3C84.
    Link https://iopscience.iop.org/article/10.3847/1538-4357/ab88a0
    Attache file 200521_Wajima_2020_ApJ_895_35.pdf
  • 2020-05
    A Massive Molecular Torus inside a Gas-poor Circumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
    Seiji Kameno1,2 , Satoko Sawada-Satoh3 , C. M. Violette Impellizzeri1,4 , Daniel Espada5 , Naomasa Nakai6 ,
    Hajime Sugai7 , Yuichi Terashima8 , Kotaro Kohno10,11 , Minju Lee9 , and Sergio Martín1,12
    Title A Massive Molecular Torus inside a Gas-poor Circumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
    Date 2020-05
    Publication The Astrophysical Journal, Volume 895, 73 pp. (2020)
    Authors Seiji Kameno1,2 , Satoko Sawada-Satoh3 , C. M. Violette Impellizzeri1,4 , Daniel Espada5 , Naomasa Nakai6 ,
    Hajime Sugai7 , Yuichi Terashima8 , Kotaro Kohno10,11 , Minju Lee9 , and Sergio Martín1,12
    Affiliation 1 Joint ALMA Observatory, Alonso de Córdova 3107 Vitacura, Santiago 763-0355, Chile; seiji.kameno@alma.cl
    2 NAOJ Chile Observatory, Alonso de Córdova 3788, Oficina 61B, Vitacura, Santiago, Chile
    3 Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 1677-1 Yoshida, Yamaguchi-shi, Yamaguchi 753-8512, Japan
    4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22902, USA
    5 SKA Organization, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK
    6 Department of Physics, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan
    7 Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, The University of Tokyo (Kavli IPMU, WPI), 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
    8 Department of Physics, Ehime University, Matsuyama 790-8577, Japan
    9 Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching, Germany
    10 Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
    11 Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
    12 European Southern Observatory, Alonso de Córdova 3107 Vitacura, Santiago 763-0355, Chile
    Abstract We report ALMA observations of NGC 1052 to search for mass accretion in a gas-poor active galactic nucleus. We
    detected CO emission representing a rotating ring-like circumnuclear disk (CND) seen edge-on with a gas mass of
    5.3×105 Me. The CND has smaller gas mass than that in typical Seyfert galaxies with circumnuclear star
    formation and is too gas-poor to drive mass accretion onto the central engine. The continuum emission casts
    molecular absorption features of CO, HCN, HCO+, SO, SO2, CS, CN, and H2O, with H13CN and HC15N and
    vibrationally excited (v2=1) HCN and HCO+. Broader absorption line widths than CND emission-line widths
    imply the presence of a geometrically thick molecular torus with a radius of 2.4±1.3 pc and a thickness ratio
    of 0.7±0.3. We obtain an H2 column density of (3.3±0.7)×1025 cm−2 using H12CN, H13CN, and HCO+
    absorption features and adopting abundance ratios of 12C to 13C and HCO+ to H2, and we derived a torus gas mass
    of (1.3±0.3)×107 Me, which is ∼9% of the central black hole mass. The molecular gas in the torus is clumpy,
    with an estimated covering factor of 0.17+0.06. The gas density of the clumps inside the torus is inferred to be 7 −3 -0.03
    (6.4±1.3)×10 cm , which meets the excitation conditions for an H2O maser. The specific angular momentum in the torus exceeds the flat rotation curve extrapolated from that of the CND, indicating a Keplerian rotation inside a 14.4 pc sphere of influence.
    Link https://doi.org/10.3847/1538-4357/ab8bd6
    Attache file 논문_2020외부_4_A Massive Molecular Torus inside__Kameno_2020_ApJ_895_73 복사본.pdf
  • 2020-05
    Asymmetric distributions of H2O and SiO masers towards V627 Cas
    Haneul Yang ,1,2 ‹ Se-Hyung Cho,1,2 ‹ Youngjoo Yun,2 Dong-Hwan Yoon,2 Dong-Jin Kim,3 Hyosun Kim,2 Sung-Chul Yoon,1 Richard Dodson ,4 Mar ́ıa J. Rioja4,5 and Hiroshi Imai6
    Title Asymmetric distributions of H2O and SiO masers towards V627 Cas
    Date 2020-05
    Publication Monthly Notices of the Royal Astronomical Society, 495, 1284 pp. (2020)
    Authors Haneul Yang ,1,2 ‹ Se-Hyung Cho,1,2 ‹ Youngjoo Yun,2 Dong-Hwan Yoon,2 Dong-Jin Kim,3 Hyosun Kim,2 Sung-Chul Yoon,1 Richard Dodson ,4 Mar ́ıa J. Rioja4,5 and Hiroshi Imai6
    Affiliation 1Astronomy program, Department of Physics and Astronomy, Seoul National University, Gwanakgu, Seoul 08826, Korea
    2Radio Astronomy Division, Korea Astronomy and Space Science Institute, Yuseong–gu, Daejeon 34055, Korea
    3Max-Planck-Institut fu ̈r Radioastronomie, Auf dem Hu ̈gel 69, Bonn D-53121, Germany
    4International Center for Radio Astronomy Research, M468, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia 5Observatorio AstronA ̃s ̧mico Nacional (IGN), Alfonso XII, 3 y 5, Madrid E-28014, Spain
    6Center of General Education, Kagoshima University, Korimoto 1-21-30, Kagoshima 890-0065, Japan
    Abstract We performed simultaneous observations of the H2 O 61,6 − 52,3 (22.235080 GHz) and SiO v = 1, 2, J = 1 → 0, SiO v = 1, J = 2 → 1, 3 → 2 (43.122080, 42.820587, 86.243442, and 129.363359 GHz) masers towards the suspected D-type symbiotic star, V627 Cas, using the Korean VLBI Network. Here, we present astrometrically registered maps of the H2O and SiO v = 1, 2, J = 1 → 0, SiO v = 1, J = 2 → 1 masers for five epochs from January 2016 to June 2018. Distributions of the SiO maser spots do not show clear ring-like structures, and those of the H2O maser are biased towards the north–north-west to west with respect to the SiO maser features according to observational epochs. These asymmetric distributions of H2O and SiO masers are discussed based on two scenarios of a bipolar outflow and the presence of the hot companion, a white dwarf, in V627 Cas. We carried out ring fitting of SiO v = 1, and v = 2 masers and estimated the expected position of the cool red giant. The ring radii of the SiO v = 1 maser are slightly larger than those of the SiO v = 2 maser, as previously known. Our assumption for the physical size of the SiO maser ring of V627 Cas to be the typical size of a SiO maser ring radius (∼4 au) of red giants yields the distance of V627 Cas to be ∼1 kpc.
    Link https://watermark.silverchair.com/stz3608.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAqowggKmBgkqhkiG9w0BBwagggKXMIICkwIBADCCAowGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQM54mx3V0iFxcgUoeU
    Attache file 200505_Yang_MNRAS_staa1206.pdf
  • 2020-04
    Constraining the Einstein equivalence principle with multi-wavelength observations of polarized blazars
    Shuang-Xi Yi,1‹ Yuan-Chuan Zou ,2‹ Xuan Yang,2,3 Bin Liao2 and Shao-Wen Wei4
    Title Constraining the Einstein equivalence principle with multi-wavelength observations of polarized blazars
    Date 2020-04
    Publication
    Authors Shuang-Xi Yi,1‹ Yuan-Chuan Zou ,2‹ Xuan Yang,2,3 Bin Liao2 and Shao-Wen Wei4
    Affiliation 1School of Physics and Physical Engineering, Qufu Normal University, Qufu 273165, China
    2School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
    3Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008, China
    4Institute of Theoretical Physics & Research Center of Gravitation, Lanzhou University, Lanzhou 730000, China
    Abstract In this paper, we present a novel method to test the Einstein equivalence principle (EEP) using (simultaneous) multi-wavelength radio observations of polarized blazars. We analyse simultaneous multi-wavelength polarization observations of 3C 279 at 22, 43, and 86 GHz obtained by two antennas of the Korean VLBI Network. We obtained 15 groups of polarization data, and applied the Metropolis–Hastings Markov chain (MHMC) to simulate the parameters when considering the EEP effect and the simplest form of Faraday rotation (single external Faraday screen). The final results show the constraint of the parametrized post-Newtonian (PPN) parameter γ discrepancy as
    Link MNRAS, Volume 493, 1782 pp. (2020)
    Attache file 논문_2020외부_6_0414_staa369_Constraining the Einstein equivalence principle.pdf
  • 2020-03
    BAT AGN spectroscopic survey - XV: the high frequency radio cores of ultra-hard X-ray selected AGN
    Krista Lynne Smith,1ܠ Richard F. Mushotzky,2 Michael Koss ,3
    Benny Trakhtenbrot ,4 Claudio Ricci,5,6 O. Ivy Wong,7 Franz E. Bauer,5,8,9
    Federica Ricci ,5 Stuart Vogel,2 Daniel Stern,10 Meredith C. Powell,11 C. Meg Urry,11 Fiona Harrison,12 Julian Mejia-Restrepo ,13 Kyuseok Oh,14,15‡ Junhyun Baek16
    and Aeree Chung16
    Title BAT AGN spectroscopic survey - XV: the high frequency radio cores of ultra-hard X-ray selected AGN
    Date 2020-03
    Publication Monthly Notices of the Royal Astronomical Society, Volume 492, issue 3, 4216, 14 pp. (2020)
    Authors Krista Lynne Smith,1ܠ Richard F. Mushotzky,2 Michael Koss ,3
    Benny Trakhtenbrot ,4 Claudio Ricci,5,6 O. Ivy Wong,7 Franz E. Bauer,5,8,9
    Federica Ricci ,5 Stuart Vogel,2 Daniel Stern,10 Meredith C. Powell,11 C. Meg Urry,11 Fiona Harrison,12 Julian Mejia-Restrepo ,13 Kyuseok Oh,14,15‡ Junhyun Baek16
    and Aeree Chung16
    Affiliation 1 KIPAC at SLAC, Stanford University, Menlo Park, CA 94025, USA 2Department of Astronomy, University of Maryland, College Park, MD 20742, USA
    2 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
    3 Eureka Scientific Inc., 2452 Delmer St. Suite 100, Oakland, CA 94602, USA
    4 School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
    5 Instituto de Astrof ́ısica and Centro de Astroingenier ́ıa, Facultad de F ́ısica, Pontificia Universidad Cato ́lica de Chile,
    Casilla 306, Santiago 22, Chile 6Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
    6 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
    7 ICRAR, The University of Western Australia, Crawley, Perth 6009, Western Australia
    8 Millennium Institute of Astrophysics (MAS), Nuncio Monsen ̃ or So ́ tero Sanz 100, Providencia, Santiago, Chile
    9 Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
    10 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-224, Pasadena, CA 91109, USA
    11 Yale Center for Astronomy and Astrophysics, and Physics Depart- ment, Yale University, P.O. Box 2018120, New Haven, CT 06520-8120, USA
    12 Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
    13 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Victacura, Santiago, Chile
    14 Department of Astronomy, Kyoto
    Sakyo-ku, Kyoto 606-8502, Japan
    15 Korea Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
    16 Department of Astronomy, Yonsei University, 50 Yonsei-ro, Seodaemun- gu, Seoul 03722, Republic of Korea
    Abstract We have conducted 22 GHz radio imaging at 1 arcsec resolution of 100 low-redshift AGN selected at 14–195 keV by the Swift-BAT. We find a radio core detection fraction of 96 per cent, much higher than lower frequency radio surveys. Of the 96 radio-detected AGN, 55 have compact morphologies, 30 have morphologies consistent with nuclear star formation, and 11 have sub-kpc to kpc-scale jets. We find that the total radio power does not distinguish between nuclear star formation and jets as the origin of the radio emission. For 87 objects, we use optical spectroscopy to test whether AGN physical parameters are distinct between radio morphological types. We find that X-ray luminosities tend to be higher if the 22 GHz morphology is jet-like, but find no significant difference in other physical parameters. We find that the relationship between the X-ray and core radio luminosities is consistent with the LR/LX ∼ 10−5 of coronally active stars. We further find that the canonical fundamental planes of black hole activity systematically overpredict our radio luminosities, particularly for objects with star formation morphologies.
    Link https://academic.oup.com/mnras
    Attache file 논문02-오규석_stz3608.pdf
  • 2020-02
    East Asia VLBI Network observations of the TeV Gamma-Ray Burst 190114C
    Tao An a,h, Om Sharan Salafia c, Yingkang Zhang a,b, Giancarlo Ghirlanda c, Gabriele Giovannini d,e, Marcello Giroletti d, Kazuhiro Hada f, Giulia Migliori d,e, Monica Orienti d, Bong Won Sohn g
    Title East Asia VLBI Network observations of the TeV Gamma-Ray Burst 190114C
    Date 2020-02
    Publication Science Bulletin, Short Communication, 65, 267 pp. (2020)
    Authors Tao An a,h, Om Sharan Salafia c, Yingkang Zhang a,b, Giancarlo Ghirlanda c, Gabriele Giovannini d,e, Marcello Giroletti d, Kazuhiro Hada f, Giulia Migliori d,e, Monica Orienti d, Bong Won Sohn g
    Affiliation a Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China b University of Chinese Academy of Sciences, Beijing 100049, China
    c Osserv Astron Brera, Ist Nazl Astrofis, Via E Bianchi 46, Merate I23807, Italy
    d Ist Nazl Astrofis, Ist Radioastron, Bologna I40129, Italy
    e Department of Physics and Astronomy, University of Bologna, Bologna I40129, Italy
    f National Astronomical Observatory of Japan, Tokyo 181-8588, Japan
    g Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea
    h Key laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, China
    Abstract N/A (short communication)
    Link https://www.sciencedirect.com/science/article/pii/S2095927319306553?via%3Dihub
    Attache file 200226_anTao_ScinceBulletin-ShortComm_65_267.pdf

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