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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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Valyavin G, Shulyak D, Wade GA, Antonyuk K, Zharikov SV, Galazutdinov GA, Plachinda S, Bagnulo S, Machado LF, Alvarez M, Clark DM, Lopez JM, Hiriart D, Han I, Jeon YB, Zurita C, Mujica R, Burlakova T, Szeifert T, Burenkov A. Suppression of cooling by strong magnetic fields in white dwarf stars. Nature 2014; 515:88-91. [PMID: 25327247 DOI: 10.1038/nature13836] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Accepted: 09/02/2014] [Indexed: 11/09/2022]
Abstract
Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.
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Affiliation(s)
- G Valyavin
- Special Astrophysical Observatory of Russian Academy of Science, Nizhnij Arkhyz, Zelenchukskiy region, Karachai-Cherkessian Republic 369167, Russia
| | - D Shulyak
- Institute for Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - G A Wade
- Department of Physics, Royal Military College of Canada, PO Box 17000 Station Forces, Kingston, Ontario, K7K 7B4, Canada
| | - K Antonyuk
- Crimean Astrophysical Observatory, Nauchny, Crimea 98409, Ukraine
| | - S V Zharikov
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - G A Galazutdinov
- 1] Instituto de Astronomía, Universidad Catolica del Norte, Avenida Angamos 0610, Antofagasta, Chile [2] Pulkovo Observatory, Pulkovskoe Shosse 65/1, Saint-Petersburg 196140, Russia
| | - S Plachinda
- Crimean Astrophysical Observatory, Nauchny, Crimea 98409, Ukraine
| | - S Bagnulo
- Armagh Observatory, College Hill, Armagh BT61 9DG, UK
| | - L Fox Machado
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - M Alvarez
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - D M Clark
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - J M Lopez
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - D Hiriart
- Instituto de Astronomía, Observatorio Astronómico Nacional San Pedro Martir (SPM), Universidad Nacional Autónoma de México, 22860 Ensenada, Baja California, Mexico
| | - Inwoo Han
- Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon 305-348, South Korea
| | - Young-Beom Jeon
- Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon 305-348, South Korea
| | - C Zurita
- 1] Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain [2] Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
| | - R Mujica
- Instituto Nacional de Astrofísica, Óptica y Electróníca, Apartado Postal 51 y 216, 72000 Tonantzintla, Pueblo, Mexico
| | - T Burlakova
- Special Astrophysical Observatory of Russian Academy of Science, Nizhnij Arkhyz, Zelenchukskiy region, Karachai-Cherkessian Republic 369167, Russia
| | - T Szeifert
- European Southern Observatory, Alonso de Córdova 3107, Santiago, Chile
| | - A Burenkov
- Special Astrophysical Observatory of Russian Academy of Science, Nizhnij Arkhyz, Zelenchukskiy region, Karachai-Cherkessian Republic 369167, Russia
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