Korean VLBI Network (KVN)

Recent Papers using KVN

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  • 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
  • 2020-05
    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
    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
  • 2020-03
    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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