1
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Jorstad SG, Marscher AP, Raiteri CM, Villata M, Weaver ZR, Zhang H, Dong L, Gómez JL, Perel MV, Savchenko SS, Larionov VM, Carosati D, Chen WP, Kurtanidze OM, Marchini A, Matsumoto K, Mortari F, Aceti P, Acosta-Pulido JA, Andreeva T, Apolonio G, Arena C, Arkharov A, Bachev R, Banfi M, Bonnoli G, Borman GA, Bozhilov V, Carnerero MI, Damljanovic G, Ehgamberdiev SA, Elsässer D, Frasca A, Gabellini D, Grishina TS, Gupta AC, Hagen-Thorn VA, Hallum MK, Hart M, Hasuda K, Hemrich F, Hsiao HY, Ibryamov S, Irsmambetova TR, Ivanov DV, Joner MD, Kimeridze GN, Klimanov SA, Knött J, Kopatskaya EN, Kurtanidze SO, Kurtenkov A, Kuutma T, Larionova EG, Leonini S, Lin HC, Lorey C, Mannheim K, Marino G, Minev M, Mirzaqulov DO, Morozova DA, Nikiforova AA, Nikolashvili MG, Ovcharov E, Papini R, Pursimo T, Rahimov I, Reinhart D, Sakamoto T, Salvaggio F, Semkov E, Shakhovskoy DN, Sigua LA, Steineke R, Stojanovic M, Strigachev A, Troitskaya YV, Troitskiy IS, Tsai A, Valcheva A, Vasilyev AA, Vince O, Waller L, Zaharieva E, Chatterjee R. Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae. Nature 2022; 609:265-268. [PMID: 36071186 DOI: 10.1038/s41586-022-05038-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 06/28/2022] [Indexed: 12/24/2022]
Abstract
Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales1-3. This variability seems mostly random, although some quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare4 in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet5, plasma instabilities6,7 or orbital motion in an accretion disc7,8. Here we report results of intense optical and γ-ray flux monitoring of BL Lacertae (BL Lac) during a dramatic outburst in 2020 (ref. 9). BL Lac, the prototype of a subclass of blazars10, is powered by a 1.7 × 108 MSun (ref. 11) black hole in an elliptical galaxy (distance = 313 megaparsecs (ref. 12)). Our observations show QPOs of optical flux and linear polarization, and γ-ray flux, with cycles as short as approximately 13 h during the highest state of the outburst. The QPO properties match the expectations of current-driven kink instabilities6 near a recollimation shock about 5 parsecs (pc) from the black hole in the wake of an apparent superluminal feature moving down the jet. Such a kink is apparent in a microwave Very Long Baseline Array (VLBA) image.
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Affiliation(s)
- S G Jorstad
- Institute for Astrophysical Research, Boston University, Boston, MA, USA. .,Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia.
| | - A P Marscher
- Institute for Astrophysical Research, Boston University, Boston, MA, USA
| | - C M Raiteri
- INAF, Osservatorio Astrofisico di Torino, Torino, Italy
| | - M Villata
- INAF, Osservatorio Astrofisico di Torino, Torino, Italy
| | - Z R Weaver
- Institute for Astrophysical Research, Boston University, Boston, MA, USA
| | - H Zhang
- NASA Postdoctoral Program Fellow, Greenbelt, MD, USA.,NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - L Dong
- Department of Physics, Purdue University, West Lafayette, IN, USA
| | - J L Gómez
- Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain
| | - M V Perel
- St. Petersburg State University, St. Petersburg, Russia
| | - S S Savchenko
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia.,Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Russia.,Pulkovo Observatory, St. Petersburg, Russia
| | - V M Larionov
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia.,Pulkovo Observatory, St. Petersburg, Russia
| | - D Carosati
- EPT Observatories, Tijarafe, La Palma, Spain.,INAF, TNG Fundación Galileo Galilei, La Palma, Spain
| | - W P Chen
- Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan
| | - O M Kurtanidze
- Abastumani Observatory, Mt. Kanobili, Abastumani, Georgia.,Engelhardt Astronomical Observatory, Kazan Federal University, Tatarstan, Russia.,Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Heidelberg, Germany
| | - A Marchini
- Astronomical Observatory, Department of Physical Sciences, Earth and Environment, University of Siena, Siena, Italy
| | - K Matsumoto
- Astronomical Institute, Osaka Kyoiku University, Kashiwara, Japan
| | | | - P Aceti
- Osservatorio Astronomico Città di Seveso, Seveso, Italy.,Department of Aerospace Science and Technology, Politecnico di Milano, Milano, Italy
| | - J A Acosta-Pulido
- Instituto de Astrofísica de Canarias and Dpto. de Astrofísica, Universidad de La Laguna, Tenerife, Spain
| | - T Andreeva
- Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg, Russia
| | - G Apolonio
- Department of Physics and Astronomy, Brigham Young University, Provo, UT, USA
| | - C Arena
- Gruppo Astrofili Catanesi (GAC), Catania, Italy
| | - A Arkharov
- Pulkovo Observatory, St. Petersburg, Russia
| | - R Bachev
- Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - M Banfi
- Osservatorio Astronomico Città di Seveso, Seveso, Italy
| | - G Bonnoli
- Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain.,Astronomical Observatory, Department of Physical Sciences, Earth and Environment, University of Siena, Siena, Italy.,INAF-Osservatorio Astronomico di Brera, Merate, Italy
| | - G A Borman
- Crimean Astrophysical Observatory RAS, Bakhchisaray, Crimea
| | - V Bozhilov
- Department of Astronomy, Faculty of Physics, University of Sofia, Sofia, Bulgaria
| | - M I Carnerero
- INAF, Osservatorio Astrofisico di Torino, Torino, Italy
| | | | - S A Ehgamberdiev
- Ulugh Beg Astronomical Institute, Tashkent, Uzbekistan.,National University of Uzbekistan, Tashkent, Uzbekistan
| | - D Elsässer
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany.,Department of Physics, TU Dortmund University, Dortmund, Germany
| | - A Frasca
- INAF-Osservatorio Astrofisico di Catania, Catania, Italy
| | | | - T S Grishina
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - A C Gupta
- Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India
| | - V A Hagen-Thorn
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - M K Hallum
- Institute for Astrophysical Research, Boston University, Boston, MA, USA
| | - M Hart
- Institute for Astrophysical Research, Boston University, Boston, MA, USA
| | - K Hasuda
- Department of Physical Sciences, Aoyama Gakuin University, Tokyo, Japan
| | - F Hemrich
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - H Y Hsiao
- Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan
| | - S Ibryamov
- Department of Physics and Astronomy, Faculty of Natural Sciences, University of Shumen, Shumen, Bulgaria
| | - T R Irsmambetova
- Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - D V Ivanov
- Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg, Russia
| | - M D Joner
- Department of Physics and Astronomy, Brigham Young University, Provo, UT, USA
| | - G N Kimeridze
- Abastumani Observatory, Mt. Kanobili, Abastumani, Georgia
| | | | - J Knött
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - E N Kopatskaya
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - S O Kurtanidze
- Abastumani Observatory, Mt. Kanobili, Abastumani, Georgia.,Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Heidelberg, Germany
| | - A Kurtenkov
- Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - T Kuutma
- Centro de Estudios de Física del Cosmos de Aragón, Teruel, Spain
| | - E G Larionova
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - S Leonini
- Montarrenti Observatory, Siena, Italy
| | - H C Lin
- Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan
| | - C Lorey
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - K Mannheim
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany.,Lehrstuhl für Astronomie, Universität Würzburg, Würzburg, Germany
| | - G Marino
- Gruppo Astrofili Catanesi (GAC), Catania, Italy.,Wild Boar Remote Observatory, Florence, Italy
| | - M Minev
- Department of Astronomy, Faculty of Physics, University of Sofia, Sofia, Bulgaria
| | | | - D A Morozova
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - A A Nikiforova
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia.,Pulkovo Observatory, St. Petersburg, Russia
| | - M G Nikolashvili
- Abastumani Observatory, Mt. Kanobili, Abastumani, Georgia.,Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Heidelberg, Germany
| | - E Ovcharov
- Department of Astronomy, Faculty of Physics, University of Sofia, Sofia, Bulgaria
| | - R Papini
- Wild Boar Remote Observatory, Florence, Italy
| | - T Pursimo
- Nordic Optical Telescope, Santa Cruz de Tenerife, Spain.,Department of Physics and Astronomy, Aarhus University, Aarhus C, Denmark
| | - I Rahimov
- Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg, Russia
| | - D Reinhart
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - T Sakamoto
- Department of Physical Sciences, Aoyama Gakuin University, Tokyo, Japan
| | - F Salvaggio
- Gruppo Astrofili Catanesi (GAC), Catania, Italy.,Wild Boar Remote Observatory, Florence, Italy
| | - E Semkov
- Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | | | - L A Sigua
- Abastumani Observatory, Mt. Kanobili, Abastumani, Georgia
| | - R Steineke
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - M Stojanovic
- Astronomical Observatory Belgrade, Belgrade, Serbia
| | - A Strigachev
- Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Y V Troitskaya
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - I S Troitskiy
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - A Tsai
- Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan
| | - A Valcheva
- Department of Astronomy, Faculty of Physics, University of Sofia, Sofia, Bulgaria
| | - A A Vasilyev
- Astronomical Institute, St. Petersburg State University, St. Petersburg, Russia
| | - O Vince
- Astronomical Observatory Belgrade, Belgrade, Serbia
| | - L Waller
- Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler am FKG, Würzburg, Germany
| | - E Zaharieva
- Department of Astronomy, Faculty of Physics, University of Sofia, Sofia, Bulgaria
| | - R Chatterjee
- Department of Physics, Presidency University, Kolkata, India
| |
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2
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Liodakis I, Marscher AP, Agudo I, Berdyugin AV, Bernardos MI, Bonnoli G, Borman GA, Casadio C, Casanova V, Cavazzuti E, Rodriguez Cavero N, Di Gesu L, Di Lalla N, Donnarumma I, Ehlert SR, Errando M, Escudero J, García-Comas M, Agís-González B, Husillos C, Jormanainen J, Jorstad SG, Kagitani M, Kopatskaya EN, Kravtsov V, Krawczynski H, Lindfors E, Larionova EG, Madejski GM, Marin F, Marchini A, Marshall HL, Morozova DA, Massaro F, Masiero JR, Mawet D, Middei R, Millar-Blanchaer MA, Myserlis I, Negro M, Nilsson K, O’Dell SL, Omodei N, Pacciani L, Paggi A, Panopoulou GV, Peirson AL, Perri M, Petrucci PO, Poutanen J, Puccetti S, Romani RW, Sakanoi T, Savchenko SS, Sota A, Tavecchio F, Tinyanont S, Vasilyev AA, Weaver ZR, Zhovtan AV, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Marco A, Doroshenko V, Dovčiak M, Enoto T, Evangelista Y, Fabiani S, Ferrazzoli R, Garcia JA, Gunji S, Hayashida K, Heyl J, Iwakiri W, Karas V, Kitaguchi T, Kolodziejczak JJ, La Monaca F, Latronico L, Maldera S, Manfreda A, Marinucci A, Matt G, Mitsuishi I, Mizuno T, Muleri F, Ng SCY, Oppedisano C, Papitto A, Pavlov GG, Pesce-Rollins M, Pilia M, Possenti A, Ramsey BD, Rankin J, Ratheesh A, Sgró C, Slane P, Soffitta P, Spandre G, Tamagawa T, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov S, Turolla R, Vink J, Weisskopf MC, Wu K, Xie F, Zane S. Polarized blazar X-rays imply particle acceleration in shocks. Nature 2022; 611:677-681. [PMID: 36418451 PMCID: PMC9684068 DOI: 10.1038/s41586-022-05338-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 09/12/2022] [Indexed: 11/24/2022]
Abstract
Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier1-3, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree ΠX of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock.
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Affiliation(s)
- Ioannis Liodakis
- grid.1374.10000 0001 2097 1371Finnish Centre for Astronomy with ESO, FI-20014, University of Turku, Turku, Finland
| | - Alan P. Marscher
- grid.189504.10000 0004 1936 7558Institute for Astrophysical Research, Boston University, Boston, MA USA
| | - Iván Agudo
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Andrei V. Berdyugin
- grid.1374.10000 0001 2097 1371Department of Physics and Astronomy, University of Turku, Turku, Finland
| | - Maria I. Bernardos
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Giacomo Bonnoli
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain ,grid.450217.5INAF Osservatorio Astronomico di Brera, Merate (LC), Italy
| | - George A. Borman
- Crimean Astrophysical Observatory RAS, P/O Nauchny, Nauchnij, Crimea
| | - Carolina Casadio
- grid.4834.b0000 0004 0635 685XInstitute of Astrophysics, Foundation for Research and Technology - Hellas, Voutes, Heraklion, Greece ,grid.8127.c0000 0004 0576 3437Department of Physics, University of Crete, Heraklion, Greece
| | - Víctor Casanova
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Elisabetta Cavazzuti
- grid.423784.e0000 0000 9801 3133Agenzia Spaziale Italiana, Via del Politecnico snc, Roma, Italy
| | - Nicole Rodriguez Cavero
- grid.4367.60000 0001 2355 7002Physics Department and McDonnell Center for the Space Sciences, Washington University in St Louis, St Louis, MO USA
| | - Laura Di Gesu
- grid.423784.e0000 0000 9801 3133Agenzia Spaziale Italiana, Via del Politecnico snc, Roma, Italy
| | - Niccoló Di Lalla
- grid.168010.e0000000419368956Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA USA
| | - Immacolata Donnarumma
- grid.423784.e0000 0000 9801 3133Agenzia Spaziale Italiana, Via del Politecnico snc, Roma, Italy
| | - Steven R. Ehlert
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Manel Errando
- grid.4367.60000 0001 2355 7002Physics Department and McDonnell Center for the Space Sciences, Washington University in St Louis, St Louis, MO USA
| | - Juan Escudero
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Maya García-Comas
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Beatriz Agís-González
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - César Husillos
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | - Jenni Jormanainen
- grid.1374.10000 0001 2097 1371Finnish Centre for Astronomy with ESO, FI-20014, University of Turku, Turku, Finland ,grid.1374.10000 0001 2097 1371Department of Physics and Astronomy, University of Turku, Turku, Finland
| | - Svetlana G. Jorstad
- grid.189504.10000 0004 1936 7558Institute for Astrophysical Research, Boston University, Boston, MA USA ,grid.15447.330000 0001 2289 6897Laboratory of Observational Astrophysics, St Petersburg University, St Petersburg, Russia
| | - Masato Kagitani
- grid.69566.3a0000 0001 2248 6943Graduate School of Sciences, Tohoku University, Sendai, Japan
| | - Evgenia N. Kopatskaya
- grid.15447.330000 0001 2289 6897Astronomical Institute, St Petersburg State University, St Petersburg, Russia
| | - Vadim Kravtsov
- grid.1374.10000 0001 2097 1371Department of Physics and Astronomy, University of Turku, Turku, Finland
| | - Henric Krawczynski
- grid.4367.60000 0001 2355 7002Physics Department and McDonnell Center for the Space Sciences, Washington University in St Louis, St Louis, MO USA
| | - Elina Lindfors
- grid.1374.10000 0001 2097 1371Finnish Centre for Astronomy with ESO, FI-20014, University of Turku, Turku, Finland
| | - Elena G. Larionova
- grid.15447.330000 0001 2289 6897Astronomical Institute, St Petersburg State University, St Petersburg, Russia
| | - Grzegorz M. Madejski
- grid.168010.e0000000419368956Kavli Institute for Particle Astrophysics and Cosmology, Stanford University and SLAC, Menlo Park, CA USA
| | - Frédéric Marin
- grid.440483.f0000 0000 9383 4469Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, Strasbourg, France
| | - Alessandro Marchini
- grid.9024.f0000 0004 1757 4641Department of Physical Sciences, Earth and Environment, Astronomical Observatory, University of Siena, Siena, Italy
| | - Herman L. Marshall
- grid.116068.80000 0001 2341 2786MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA USA
| | - Daria A. Morozova
- grid.15447.330000 0001 2289 6897Astronomical Institute, St Petersburg State University, St Petersburg, Russia
| | - Francesco Massaro
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy ,grid.7605.40000 0001 2336 6580Dipartimento di Fisica, Universitá degli Studi di Torino, Torino, Italy
| | | | - Dimitri Mawet
- grid.20861.3d0000000107068890California Institute of Technology, Pasadena, CA USA
| | - Riccardo Middei
- grid.423784.e0000 0000 9801 3133Space Science Data Center, Agenzia Spaziale Italiana, Roma, Italy ,grid.463298.20000 0001 2168 8201INAF Osservatorio Astronomico di Roma, Monte Porzio Catone (RM), Italy
| | | | | | - Michela Negro
- Center for Research and Exploration in Space Science and Technology (CRESST), Greenbelt, MD USA ,grid.266673.00000 0001 2177 1144Department of Physics and Center for Space Sciences and Technology, University of Maryland Baltimore County, Baltimore, MD USA
| | - Kari Nilsson
- grid.1374.10000 0001 2097 1371Finnish Centre for Astronomy with ESO, FI-20014, University of Turku, Turku, Finland
| | - Stephen L. O’Dell
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Nicola Omodei
- grid.168010.e0000000419368956Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA USA
| | - Luigi Pacciani
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Alessandro Paggi
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy ,grid.7605.40000 0001 2336 6580Dipartimento di Fisica, Universitá degli Studi di Torino, Torino, Italy ,grid.436940.cINAF-Osservatorio Astrofisico di Torino, Pino Torinese, Italy
| | | | - Abel L. Peirson
- grid.168010.e0000000419368956Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA USA
| | - Matteo Perri
- grid.423784.e0000 0000 9801 3133Space Science Data Center, Agenzia Spaziale Italiana, Roma, Italy ,grid.463298.20000 0001 2168 8201INAF Osservatorio Astronomico di Roma, Monte Porzio Catone (RM), Italy
| | | | - Juri Poutanen
- grid.1374.10000 0001 2097 1371Department of Physics and Astronomy, University of Turku, Turku, Finland ,grid.426428.e0000 0004 0405 8736Space Research Institute of the Russian Academy of Sciences, Moscow, Russia
| | - Simonetta Puccetti
- grid.423784.e0000 0000 9801 3133Agenzia Spaziale Italiana, Via del Politecnico snc, Roma, Italy
| | - Roger W. Romani
- grid.168010.e0000000419368956Department of Physics and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA USA
| | - Takeshi Sakanoi
- grid.69566.3a0000 0001 2248 6943Graduate School of Sciences, Tohoku University, Sendai, Japan
| | - Sergey S. Savchenko
- grid.15447.330000 0001 2289 6897Astronomical Institute, St Petersburg State University, St Petersburg, Russia ,grid.4886.20000 0001 2192 9124Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Russia ,grid.437494.90000 0000 9168 8058Pulkovo Observatory, St Petersburg, Russia
| | - Alfredo Sota
- grid.450285.e0000 0004 1793 7043Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, Spain
| | | | - Samaporn Tinyanont
- grid.205975.c0000 0001 0740 6917University of California Santa Cruz, Santa Cruz, CA USA
| | - Andrey A. Vasilyev
- grid.15447.330000 0001 2289 6897Astronomical Institute, St Petersburg State University, St Petersburg, Russia
| | - Zachary R. Weaver
- grid.189504.10000 0004 1936 7558Institute for Astrophysical Research, Boston University, Boston, MA USA
| | - Alexey V. Zhovtan
- Crimean Astrophysical Observatory RAS, P/O Nauchny, Nauchnij, Crimea
| | - Lucio A. Antonelli
- grid.423784.e0000 0000 9801 3133Space Science Data Center, Agenzia Spaziale Italiana, Roma, Italy ,grid.463298.20000 0001 2168 8201INAF Osservatorio Astronomico di Roma, Monte Porzio Catone (RM), Italy
| | - Matteo Bachetti
- grid.437052.70000 0001 0096 8079INAF Osservatorio Astronomico di Cagliari, Selargius (CA), Italy
| | - Luca Baldini
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy ,grid.5395.a0000 0004 1757 3729Dipartimento di Fisica, Universitá di Pisa, Pisa, Italy
| | - Wayne H. Baumgartner
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Ronaldo Bellazzini
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Stefano Bianchi
- grid.8509.40000000121622106Dipartimento di Matematica e Fisica, Universitá degli Studi Roma Tre, Roma, Italy
| | - Stephen D. Bongiorno
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Raffaella Bonino
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy ,grid.7605.40000 0001 2336 6580Dipartimento di Fisica, Universitá degli Studi di Torino, Torino, Italy
| | - Alessandro Brez
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Niccoló Bucciantini
- grid.426239.80000 0000 9176 4495INAF Osservatorio Astrofisico di Arcetri, Firenze, Italy ,grid.8404.80000 0004 1757 2304Dipartimento di Fisica e Astronomia, Universitá degli Studi di Firenze, Sesto Fiorentino (FI), Italy ,grid.470204.5Q30265285Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, Sesto Fiorentino (FI), Italy
| | - Fiamma Capitanio
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Simone Castellano
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Stefano Ciprini
- grid.423784.e0000 0000 9801 3133Space Science Data Center, Agenzia Spaziale Italiana, Roma, Italy ,grid.470219.9Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata, Roma, Italy
| | - Enrico Costa
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Alessandra De Rosa
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Ettore Del Monte
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Alessandro Di Marco
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Victor Doroshenko
- grid.426428.e0000 0004 0405 8736Space Research Institute of the Russian Academy of Sciences, Moscow, Russia ,grid.10392.390000 0001 2190 1447Institut für Astronomie und Astrophysik, Tübingen, Germany
| | - Michal Dovčiak
- grid.423799.20000 0004 0385 3578Astronomical Institute of the Czech Academy of Sciences, Ondřejov, Czech Republic
| | - Teruaki Enoto
- grid.7597.c0000000094465255RIKEN Cluster for Pioneering Research, Saitama, Japan
| | - Yuri Evangelista
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Sergio Fabiani
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Riccardo Ferrazzoli
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Javier A. Garcia
- grid.20861.3d0000000107068890California Institute of Technology, Pasadena, CA USA
| | - Shuichi Gunji
- grid.268394.20000 0001 0674 7277Yamagata University, Yamagata-shi, Japan
| | | | - Jeremy Heyl
- grid.17091.3e0000 0001 2288 9830University of British Columbia, Vancouver, British Columbia Canada
| | - Wataru Iwakiri
- grid.443595.a0000 0001 2323 0843Department of Physics, Faculty of Science and Engineering, Chuo University, Tokyo, Japan
| | - Vladimir Karas
- grid.423799.20000 0004 0385 3578Astronomical Institute of the Czech Academy of Sciences, Ondřejov, Czech Republic
| | - Takao Kitaguchi
- grid.7597.c0000000094465255RIKEN Cluster for Pioneering Research, Saitama, Japan
| | | | - Fabio La Monaca
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Luca Latronico
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy
| | - Simone Maldera
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy
| | - Alberto Manfreda
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Andrea Marinucci
- grid.423784.e0000 0000 9801 3133Agenzia Spaziale Italiana, Via del Politecnico snc, Roma, Italy
| | - Giorgio Matt
- grid.8509.40000000121622106Dipartimento di Matematica e Fisica, Universitá degli Studi Roma Tre, Roma, Italy
| | - Ikuyuki Mitsuishi
- grid.27476.300000 0001 0943 978XGraduate School of Science, Division of Particle and Astrophysical Science, Nagoya University, Nagoya, Japan
| | - Tsunefumi Mizuno
- grid.257022.00000 0000 8711 3200Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima, Japan
| | - Fabio Muleri
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Stephen C.-Y. Ng
- grid.194645.b0000000121742757Department of Physics, University of Hong Kong, Pokfulam, Hong Kong
| | - Chiara Oppedisano
- grid.470222.10000 0004 7471 9712Istituto Nazionale di Fisica Nucleare, , Sezione di Torino, Torino, Italy
| | - Alessandro Papitto
- grid.463298.20000 0001 2168 8201INAF Osservatorio Astronomico di Roma, Monte Porzio Catone (RM), Italy
| | - George G. Pavlov
- grid.29857.310000 0001 2097 4281Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA USA
| | | | - Maura Pilia
- grid.437052.70000 0001 0096 8079INAF Osservatorio Astronomico di Cagliari, Selargius (CA), Italy
| | - Andrea Possenti
- grid.437052.70000 0001 0096 8079INAF Osservatorio Astronomico di Cagliari, Selargius (CA), Italy
| | - Brian D. Ramsey
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - John Rankin
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Ajay Ratheesh
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Carmelo Sgró
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Patrick Slane
- grid.455754.20000 0001 1781 4754Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA USA
| | - Paolo Soffitta
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - Gloria Spandre
- grid.470216.6Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy
| | - Toru Tamagawa
- grid.7597.c0000000094465255RIKEN Cluster for Pioneering Research, Saitama, Japan
| | - Roberto Taverna
- grid.5608.b0000 0004 1757 3470Dipartimento di Fisica e Astronomia, Universitá degli Studi di Padova, Padova, Italy
| | - Yuzuru Tawara
- grid.27476.300000 0001 0943 978XGraduate School of Science, Division of Particle and Astrophysical Science, Nagoya University, Nagoya, Japan
| | - Allyn F. Tennant
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Nicolas E. Thomas
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Francesco Tombesi
- grid.6530.00000 0001 2300 0941Dipartimento di Fisica, Universitá degli Studi di Roma Tor Vergata, Roma, Italy
| | - Alessio Trois
- grid.437052.70000 0001 0096 8079INAF Osservatorio Astronomico di Cagliari, Selargius (CA), Italy
| | - Sergey Tsygankov
- grid.1374.10000 0001 2097 1371Department of Physics and Astronomy, University of Turku, Turku, Finland ,grid.426428.e0000 0004 0405 8736Space Research Institute of the Russian Academy of Sciences, Moscow, Russia
| | - Roberto Turolla
- grid.5608.b0000 0004 1757 3470Dipartimento di Fisica e Astronomia, Universitá degli Studi di Padova, Padova, Italy ,grid.83440.3b0000000121901201Mullard Space Science Laboratory, University College London, Dorking, UK
| | - Jacco Vink
- grid.7177.60000000084992262Anton Pannekoek Institute for Astronomy & GRAPPA, University of Amsterdam, Amsterdam, the Netherlands
| | - Martin C. Weisskopf
- grid.419091.40000 0001 2238 4912NASA Marshall Space Flight Center, Huntsville, AL USA
| | - Kinwah Wu
- grid.83440.3b0000000121901201Mullard Space Science Laboratory, University College London, Dorking, UK
| | - Fei Xie
- grid.466835.a0000 0004 1776 2255INAF Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy ,grid.256609.e0000 0001 2254 5798Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University, Nanning, China
| | - Silvia Zane
- grid.83440.3b0000000121901201Mullard Space Science Laboratory, University College London, Dorking, UK
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3
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Raiteri CM, Villata M, Acosta-Pulido JA, Agudo I, Arkharov AA, Bachev R, Baida GV, Benítez E, Borman GA, Boschin W, Bozhilov V, Butuzova MS, Calcidese P, Carnerero MI, Carosati D, Casadio C, Castro-Segura N, Chen WP, Damljanovic G, D'Ammando F, Di Paola A, Echevarría J, Efimova NV, Ehgamberdiev SA, Espinosa C, Fuentes A, Giunta A, Gómez JL, Grishina TS, Gurwell MA, Hiriart D, Jermak H, Jordan B, Jorstad SG, Joshi M, Kopatskaya EN, Kuratov K, Kurtanidze OM, Kurtanidze SO, Lähteenmäki A, Larionov VM, Larionova EG, Larionova LV, Lázaro C, Lin CS, Malmrose MP, Marscher AP, Matsumoto K, McBreen B, Michel R, Mihov B, Minev M, Mirzaqulov DO, Mokrushina AA, Molina SN, Moody JW, Morozova DA, Nazarov SV, Nikolashvili MG, Ohlert JM, Okhmat DN, Ovcharov E, Pinna F, Polakis TA, Protasio C, Pursimo T, Redondo-Lorenzo FJ, Rizzi N, Rodriguez-Coira G, Sadakane K, Sadun AC, Samal MR, Savchenko SS, Semkov E, Skiff BA, Slavcheva-Mihova L, Smith PS, Steele IA, Strigachev A, Tammi J, Thum C, Tornikoski M, Troitskaya YV, Troitsky IS, Vasilyev AA, Vince O. Blazar spectral variability as explained by a twisted inhomogeneous jet. Nature 2017; 552:374-377. [PMID: 29211720 DOI: 10.1038/nature24623] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 10/06/2017] [Indexed: 11/09/2022]
Abstract
Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions-such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution-can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle. The agreement between observations and theoretical predictions can be seen as further validation of the relativistic beaming theory.
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Affiliation(s)
- C M Raiteri
- INAF, Osservatorio Astrofisico di Torino, I-10025 Pino Torinese, Italy
| | - M Villata
- INAF, Osservatorio Astrofisico di Torino, I-10025 Pino Torinese, Italy
| | - J A Acosta-Pulido
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - I Agudo
- Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada, Spain
| | - A A Arkharov
- Pulkovo Observatory, 196140 St Petersburg, Russia
| | - R Bachev
- Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
| | - G V Baida
- Crimean Astrophysical Observatory RAS, Nauchny 298409, Russia
| | - E Benítez
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
| | - G A Borman
- Crimean Astrophysical Observatory RAS, Nauchny 298409, Russia
| | - W Boschin
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain.,INAF, TNG Fundación Galileo Galilei, E-38712 La Palma, Spain
| | - V Bozhilov
- Department of Astronomy, Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria
| | - M S Butuzova
- Crimean Astrophysical Observatory RAS, Nauchny 298409, Russia
| | - P Calcidese
- Osservatorio Astronomico della Regione Autonoma Valle d'Aosta, I-11020 Nus, Italy
| | - M I Carnerero
- INAF, Osservatorio Astrofisico di Torino, I-10025 Pino Torinese, Italy
| | - D Carosati
- INAF, TNG Fundación Galileo Galilei, E-38712 La Palma, Spain.,EPT Observatories, Tijarafe, E-38780 La Palma, Spain
| | - C Casadio
- Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada, Spain.,Max-Planck-Institut für Radioastronomie, D-53121 Bonn, Germany
| | - N Castro-Segura
- Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain.,School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
| | - W-P Chen
- Graduate Institute of Astronomy, National Central University, Jhongli City, Taoyuan County 32001, Taiwan
| | | | - F D'Ammando
- Dipartimento di Fisica e Astronomia, Università di Bologna, I-40129 Bologna, Italy.,INAF, Istituto di Radioastronomia, I-40129 Bologna, Italy
| | - A Di Paola
- INAF, Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone, Italy
| | - J Echevarría
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
| | - N V Efimova
- Pulkovo Observatory, 196140 St Petersburg, Russia
| | - Sh A Ehgamberdiev
- Ulugh Beg Astronomical Institute, Maidanak Observatory, Tashkent 100052, Uzbekistan
| | - C Espinosa
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
| | - A Fuentes
- Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada, Spain
| | - A Giunta
- INAF, Osservatorio Astronomico di Roma, I-00040 Monte Porzio Catone, Italy
| | - J L Gómez
- Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada, Spain
| | - T S Grishina
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - M A Gurwell
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
| | - D Hiriart
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
| | - H Jermak
- Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF, UK
| | - B Jordan
- School of Cosmic Physics, Dublin Institute For Advanced Studies, Dublin, Ireland
| | - S G Jorstad
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia.,Institute for Astrophysical Research, Boston University, Boston, Massachusetts 02215, USA
| | - M Joshi
- Institute for Astrophysical Research, Boston University, Boston, Massachusetts 02215, USA
| | - E N Kopatskaya
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - K Kuratov
- NNLOT, Al-Farabi Kazakh National University, Almaty, Kazakhstan.,Fesenkov Astrophysical Institute, Almaty, Kazakhstan
| | - O M Kurtanidze
- Abastumani Observatory, Mt Kanobili, 0301 Abastumani, Georgia.,Engelhardt Astronomical Observatory, Kazan Federal University, Tatarstan, Russia.,Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, 69117 Heidelberg, Germany.,Center for Astrophysics, Guangzhou University, Guangzhou 510006, China
| | - S O Kurtanidze
- Abastumani Observatory, Mt Kanobili, 0301 Abastumani, Georgia
| | - A Lähteenmäki
- Aalto University Metsähovi Radio Observatory, FI-02540 Kylmälä, Finland.,Aalto University Department of Electronics and Nanoengineering, FI-00076 Aalto, Finland.,Tartu Observatory, 61602 Tõravere, Estonia
| | - V M Larionov
- Pulkovo Observatory, 196140 St Petersburg, Russia.,Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - E G Larionova
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - L V Larionova
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - C Lázaro
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - C S Lin
- Graduate Institute of Astronomy, National Central University, Jhongli City, Taoyuan County 32001, Taiwan
| | - M P Malmrose
- Institute for Astrophysical Research, Boston University, Boston, Massachusetts 02215, USA
| | - A P Marscher
- Institute for Astrophysical Research, Boston University, Boston, Massachusetts 02215, USA
| | - K Matsumoto
- Astronomical Institute, Osaka Kyoiku University, Osaka 582-8582, Japan
| | - B McBreen
- School of Physics, University College Dublin, Dublin 4, Ireland
| | - R Michel
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
| | - B Mihov
- Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
| | - M Minev
- Department of Astronomy, Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria
| | - D O Mirzaqulov
- Ulugh Beg Astronomical Institute, Maidanak Observatory, Tashkent 100052, Uzbekistan
| | - A A Mokrushina
- Pulkovo Observatory, 196140 St Petersburg, Russia.,Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - S N Molina
- Instituto de Astrofísica de Andalucía (CSIC), E-18080 Granada, Spain
| | - J W Moody
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - D A Morozova
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - S V Nazarov
- Crimean Astrophysical Observatory RAS, Nauchny 298409, Russia
| | | | - J M Ohlert
- Michael Adrian Observatorium, Astronomie Stiftung Trebur, 65468 Trebur, Germany.,University of Applied Sciences, Technische Hochschule Mittelhessen, 61169 Friedberg, Germany
| | - D N Okhmat
- Crimean Astrophysical Observatory RAS, Nauchny 298409, Russia
| | - E Ovcharov
- Department of Astronomy, Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria
| | - F Pinna
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - T A Polakis
- Command Module Observatory, Tempe, Arizona, USA
| | - C Protasio
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - T Pursimo
- Nordic Optical Telescope, E-38700 Santa Cruz de La Palma, Spain
| | - F J Redondo-Lorenzo
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - N Rizzi
- Osservatorio Astronomico Sirio, I-70013 Castellana Grotte, Italy
| | - G Rodriguez-Coira
- Instituto de Astrofisica de Canarias (IAC), La Laguna, E-38200 Tenerife, Spain.,Departamento de Astrofisica, Universidad de La Laguna, La Laguna, E-38205 Tenerife, Spain
| | - K Sadakane
- Astronomical Institute, Osaka Kyoiku University, Osaka 582-8582, Japan
| | - A C Sadun
- Department of Physics, University of Colorado Denver, Denver, Colorado 80217-3364 USA
| | - M R Samal
- Graduate Institute of Astronomy, National Central University, Jhongli City, Taoyuan County 32001, Taiwan
| | - S S Savchenko
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - E Semkov
- Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
| | - B A Skiff
- Lowell Observatory, Flagstaff, Arizona, USA
| | - L Slavcheva-Mihova
- Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
| | - P S Smith
- Steward Observatory, University of Arizona, Tucson, Arizona, USA
| | - I A Steele
- Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF, UK
| | - A Strigachev
- Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
| | - J Tammi
- Aalto University Metsähovi Radio Observatory, FI-02540 Kylmälä, Finland
| | - C Thum
- Instituto de Radio Astronomía Milimétrica, E-18012 Granada, Spain
| | - M Tornikoski
- Aalto University Metsähovi Radio Observatory, FI-02540 Kylmälä, Finland
| | - Yu V Troitskaya
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - I S Troitsky
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - A A Vasilyev
- Astronomical Institute, St Petersburg State University, 198504 St Petersburg, Russia
| | - O Vince
- Astronomical Observatory, 11060 Belgrade, Serbia
| |
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