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351. A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279

Author

The, Fermi-LAT Collaboration and members of the 3C 279 multi-band campaign, Abdo, A. A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B. M., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bock, D. C.-J., Bogart, J. R., Bonamente, E., Borgland, A. W., Bouvier, A., Bregeon, J., Brez, A., Brigida, M., Bruel, P., Burnett, T. H., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Celik, O., Chekhtman, A., Cheung, C. C., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Collmar, W., Cominsky, L. R., Conrad, J., Corbel, S., Corbet, R., Costamante, L., Cutini, S., Dermer, C. D., de, Angelis A., de, Palma F., Digel, S. W., do, Couto e Silva E., Drell, P. S., Dubois, R., Dumora, D., Farnier, C., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fortin, P., Frailis, M., Fuhrmann, L., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giebels, B., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guillemot, L., Guiriec, S., Harding, A. K., Hays, E., Horan, D., Hughes, R. E., Iafrate, G., Itoh, R., Jackson, M. S., Johannesson, G., Johnson, A. S., Johnson, W. N., Kadler, M., Kerr, M., Knodlseder, J., Kocian, M. L., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine-Goumard, M., Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Macquart, J., Madejski, G. M., Makeev, A., Max-Moerbeck, W., Mazziotta, M. N., McConville, W., McEnery, J. E., McGlynn, S., Meurer, C., Michelson, P. F., Mitthumsiri, W., Moiseev, A. A., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nestoras, I., Nolan, P. L., Norris, J. P., Nuss, E., Okumura, A., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Parent, D., Pavlidou, V., Pearson, T. J., Pelassa, V., Pepe, M., Pesce-Rollins, M., Piron, F., Porter, T. A., Raino, S., Rando, R., Razzano, M., Readhead, A., Reimer, A., Reimer, O., Reposeur, T., Reyes, L. C., Richards, J. L., Rochester, L. S., Rodriguez, A. Y., Roth, M., Ryde, F., Sadrozinski, H. F.-W., Sanchez, D., Sander, A., Saz, Parkinson P. M., Scargle, J. D., Sgro, C., Shaw, M. S., Shrader, C., Siskind, E. J., Smith, D. A., Smith, P. D., Spandre, G., Spinelli, P., Stawarz, L., Stevenson, M., Strickman, M. S., Suson, D. J., Fukazawa, Y., Hanabata, Y., Hayashida, M., Kamae, T., Katagiri, H., Kataoka, J., Kawai, N., Mizuno, T., Ohsugi, T., Tajima, H., Takahashi, H., Takahashi, Tadayuki, Abdo, A. A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B. M., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bock, D. C. J., Bogart, J. R., Bonamente, E., Borgland, A. W., Bouvier, A., Bregeon, J., Brez, A., Brigida, M., Bruel, P., Burnett, T. H., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Celik, O., Chekhtman, A., Cheung, C. C., Chiang, J., Ciprini, S., Claus, R., Cohen Tanugi, J., Collmar, W., Cominsky, L. R., Conrad, J., Corbel, S., Corbet, R., Costamante, L., Cutini, S., Dermer, C. D., Angelis, A. d., Palma, F. d., Digel, S. W., Silva, E. D. E., Drell, P. S., Dubois, R., Dumora, D., Farnier, C., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fortin, P., Frailis, M., Fuhrmann, L., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giebels, B., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guillemot, L., Guiriec, S., Hanabata, Y., Harding, A. K., Hayashida, M., Hays, E., Horan, D., Hughes, R. E., Iafrate, G., Itoh, R., Jackson, M. S., Johannesson, G., Johnson, A. S., Johnson, W. N., Kadler, M., Kamae, T., Katagiri, H., Kataoka, J., Kawai, N., Kerr, M., Knodlseder, J., Kocian, M. L., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine Goumard, M., Longo, Francesco, Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Macquart, J., Madejski, G. M., Makeev, A., Max Moerbeck, W., Mazziotta, M. N., Mcconville, W., Mcenery, J. E., Mcglynn, S., Meurer, C., Michelson, F., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nestoras, I., Nolan, P. L., Norris, J. P., Nuss, E., Ohsugi, T., Okumura, A., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Parent, D., Pavlidou, V., Pearson, T. J., Pelassa, V., Pepe, M., Pesce Rollins, M., Piron, F., Porter, T. A., Raino, S., Rando, R., Razzano, M., Readhead, A., Reimer, A., Reimer, O., Reposeur, T., Reyes, L. C., Richards, J. L., Rochester, L. S., Rodriguez, A. Y., Roth, M., Ryde, F., Sadrozinski, H. F. W., Sanchez, D., Sander, A., Parkinson, P. M. S., Scargle, J. D., Sgro, C., Shaw, M. S., Shrader, C., Siskind, E. J., Smith, D. A., Smith, P. D., Spandre, G., Spinelli, P., Stawarz, L., Stevenson, M., Strickman, M. S., Suson, D. J., Tajima, H., Takahashi, H., Takahashi, T., Tanaka, T., Taylor, G. B., Thayer, J. B., Thayer, J. G., Thompson, D. J., Tibaldo, L., Torres, D. F., Tosti, G., Tramacere, A., Uchiyama, Y., Usher, T. L., Vasileiou, V., Vilchez, N., Vitale, V., Waite, A. P., Wang, P., Wehrle, A. E., Winer, B. L., Wood, K. S., Ylinen, T., Zensus, J. A., Ziegler, M., Uemura, M., Ikejiri, Y., Kawabata, K. S., Kino, M., Sakimoto, K., Sasada, M., Sato, S., Yamanaka, M., Villata, M., Raiteri, C. M., Agudo, I., Aller, H. D., Aller, M. F., Angelakis, E., Arkharov, A. A., Bach, U., Benitez, E., Berdyugin, A., Blinov, D. A., Boettcher, M., Buemi, C. S., Chen, W. P., Dolci, M., Dultzin, D., Efimova, N. V., Gurwell, M. A., Gusbar, C., Gomez, J. L., Heidt, J., Hiriart, D., Hovatta, T., Jorstad, S. G., Konstantinova, T. S., Kopatskaya, E. N., Koptelova, E., Kurtanidze, O. M., Lahteenmaki, A., Larionov, V. M., Larionova, E. G., Leto, P., Lin, H. C., Lindfors, E., Marscher, A. P., Mchardy, I. M., Melnichuk, D. A., Mommert, M., Nilsson, K., Paola, A. D., Reinthal, R., Richter, G. M., Roca Sogorb, M., Roustazadeh, P., Sigua, L. A., Takalo, L. O., Tornikoski, M., Trigilio, C., Troitsky, I. S., Umana, G., Villforth, C., Grainge, K., Moderski, R., Nalewajko, K., Sikora, M., Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire de Physique Théorique et Astroparticules (LPTA), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Fermi-LAT, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Active galactic nucleus, High Energy Gamma-ray Astronomy, Fermi satellite, Active Galactic Nuclei, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, 01 natural sciences, law.invention, law, 0103 physical sciences, Blazar, 010303 astronomy & astrophysics, Physics, Supermassive black hole, Multidisciplinary, ta115, ta213, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astronomy, Quasar, Optical polarization, Galaxy, Spin-flip, Astrophysics - High Energy Astrophysical Phenomena, Flare, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and gamma-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 10^5 gravitational radii., Comment: Published in Nature issued on 18 February 2010. Corresponding authors: Masaaki Hayashida and Greg Madejski

Published
2010

352. AGILE detection of a rapid gamma-ray flare from the blazar PKS 1510-089 during the GASP-WEBT monitoring

Author

Dario Gasparrini, A. W. Chen, Alan P. Marscher, P. Giommi, C. Pittori, Filippo D'Ammando, T. Froysland, A. Argan, Andrea Bulgarelli, Enrico Costa, M. Sorcia, Carla Buemi, F. Fuschino, Svetlana G. Jorstad, Massimo Rapisarda, Marco Feroci, Arnaud Ferrari, Luigi Pacciani, Uwe Bach, Corrado Trigilio, F. Boffelli, G. De Paris, Jochen Heidt, L. A. Antonelli, Deborah Dultzin, F. Perotti, Raúl Mújica, C. M. Raiteri, Lars Fuhrmann, G. Umana, D. Zanello, A. Zambra, A. Morselli, Mark Gurwell, Paolo Soffitta, Margo F. Aller, Kari Nilsson, Marco Tavani, E. Vallazza, Wen Ping Chen, Tatiana S. Konstantinova, S. Sabatini, I. M. McHardy, Ekaterina Koptelova, A. Rappoldi, M. Fiorini, Ivan Agudo, Martino Marisaldi, José L. Gómez, V. Cocco, J. M. Lopez, Valeri M. Larionov, S. Vercellone, Elina Lindfors, A. Pellizzoni, E. Del Monte, H. Y. Hsiao, G. Pucella, F. Longo, I. Lapshov, L. Salotti, Ivan S. Troitsky, A. Giuliani, Sandro Mereghetti, Paolo Lipari, L. O. Takalo, Mar Roca-Sogorb, P. W. Cattaneo, Omar M. Kurtanidze, Brian W. Taylor, G. Di Rico, M. Trifoglio, David Hiriart, S. Colafrancesco, P. Picozza, G. Barbiellini, G. Piano, Hugh D. Aller, Fulvio Gianotti, Maura Pilia, Alessio Trois, A. A. Arkharov, B. Preger, G. Di Cocco, Givi N. Kimeridze, S. Cutini, Claudio Labanti, Erika Benítez, P. Santolamazza, I. Donnarumma, Y. Evangelista, A. Di Paola, M. Galli, E. N. Kopatskaya, P. A. Caraveo, Paolo Leto, F. Verrecchia, Michael Mommert, Francesco Lazzarotto, Andrei Berdyugin, M. Pasanen, D. A. Melnichuk, M. Prest, M. Villata, D. Blinov, V. Vittorini, DAmmando F, Pucella G, Raiteri CM, Villata M, Vittorini V, Vercellone S, Donnarumma I, Longo F, Tavani M, Argan A, Barbiellini G, Boffelli F, Bulgarelli A, Caraveo P, Cattaneo PW, Chen AW, Cocco V, Costa E, Del Monte E, De Paris G, Di Cocco G, Evangelista Y, Feroci M, Ferrari A, Fiorini M, Froysland T, Fuschino F, Galli M, Gianotti F, Giuliani A, Labanti C, Lapshov I, Lazzarotto F, Lipari P, Marisaldi M, Mereghetti S, Morselli A, Pacciani L, Pellizzoni A, Perotti F, Piano G, Picozza P, Pilia M, Prest M, Rapisarda M, Rappoldi A, Sabatini S, Soffitta P, Trifoglio M, Trois A, Vallazza E, Zambra A, Zanello D, Agudo I, Aller MF, Aller HD, Arkharov AA, Bach U, Benitez E, Berdyugin A, Blinov DA, Buemi CS, Chen WP, Di Paola A, Di Rico G, Dultzin D, Fuhrmann L, Gomez JL, Gurwell MA, Jorstad SG, Heidt J, Hiriart D, Hsiao HY, Kimeridze G, Konstantinova TS, Kopatskaya EN, Koptelova E, Kurtanidze O, Larionov VM, Leto P, Lindfors E, Lopez JM, Marscher AP, McHardy IM, Melnichuk DA, Mommert M, Mujica R, Nilsson K, Pasanen M, Roca-Sogorb M, Sorcia M, Takalo LO, Taylor B, Trigilio C, Troitsky IS, Umana G, Antonelli LA, Colafrancesco S, Cutini S, Gasparrini D, Pittori C, Preger B, Santolamazza P, Verrecchia F, Giommi P, Salotti L, F., D'Ammando, G., Pucella, C. M., Raiteri, M., Villata, V., Vittorini, S., Vercellone, I., Donnarumma, Longo, Francesco, M., Tavani, A., Argan, G., Barbiellini, F., Boffelli, A., Bulgarelli, P., Caraveo, P. W., Cattaneo, A. W., Chen, V., Cocco, E., Costa, E. D., Monte, G. D., Pari, G. D., Cocco, Y., Evangelista, M., Feroci, A., Ferrari, M., Fiorini, T., Froysland, F., Fuschino, M., Galli, F., Gianotti, A., Giuliani, C., Labanti, I., Lapshov, F., Lazzarotto, P., Lipari, M., Marisaldi, S., Mereghetti, A., Morselli, L., Pacciani, A., Pellizzoni, F., Perotti, G., Piano, P., Picozza, M., Pilia, M., Prest, M., Rapisarda, A., Rappoldi, S., Sabatini, P., Soffitta, M., Trifoglio, A., Troi, E., Vallazza, A., Zambra, D., Zanello, I., Agudo, M. F., Aller, H. D., Aller, A. A., Arkharov, U., Bach, E., Benitez, A., Berdyugin, D. A., Blinov, C. S., Buemi, W. P., Chen, A. D., Paola, G. D., Rico, D., Dultzin, L., Fuhrmann, J. L., Gomez, M. A., Gurwell, S. G., Jorstad, J., Heidt, D., Hiriart, H. Y., Hsiao, G., Kimeridze, T. S., Konstantinova, E. N., Kopatskaya, E., Koptelova, O., Kurtanidze, V. M., Larionov, P., Leto, E., Lindfor, J. M., Lopez, A. P., Marscher, I. M., Mchardy, D. A., Melnichuk, M., Mommert, R., Mujica, K., Nilsson, M., Pasanen, M., Roca Sogorb, M., Sorcia, L. O., Takalo, B., Taylor, C., Trigilio, I. S., Troitsky, G., Umana, L. A., Antonelli, S., Colafrancesco, S., Cutini, D., Gasparrini, C., Pittori, B., Preger, P., Santolamazza, F., Verrecchia, P., Giommi, and L., Salotti

Subjects
Agile, Active galactic nucleus, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Radio spectrum, gamma-ray flare, High Energy Gamma-ray Astronomy, AGILE satellite, Active Galactic Nuclei, law.invention, law, quasar, Blazar, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Gamma ray, Compton scattering, Astronomy and Astrophysics, Quasar, Space and Planetary Science, gamma-rays: observations – mechanism: non-thermal – quasars: individual (PKS 1510-089), Spectral energy distribution, Astrophysics - High Energy Astrophysical Phenomena, Flare, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We report the detection by the AGILE satellite of a rapid gamma-ray flare from the powerful gamma-ray quasar PKS 1510-089, during a pointing centered on the Galactic Center region from 1 March to 30 March 2008. This source has been continuosly monitored in the radio-to-optical bands by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT). Moreover, the gamma-ray flaring episode triggered three ToO observations by the Swift satellite in three consecutive days, starting from 20 March 2008. In the period 1-16 March 2008, AGILE detected gamma-ray emission from PKS 1510-089 at a significance level of 6.2-sigma with an average flux over the entire period of (84 +/- 17) x 10^{-8} photons cm^{-2} s^{-1} for photon energies above 100 MeV. After a predefined satellite re-pointing, between 17 and 21 March 2008, AGILE detected the source at a significance level of 7.3-sigma, with an average flux (E > 100 MeV) of (134 +/- 29) x 10^{-8} photons cm^{-2} s^{-1} and a peak level of (281 +/- 68) x 10^{-8} photons cm^{-2} s^{-1} with daily integration. During the observing period January-April 2008, the source also showed an intense and variable optical activity, with several flaring episodes and a significant increase of the flux was observed at millimetric frequencies. Moreover, in the X-ray band the Swift/XRT observations seem to show an harder-when-brighter behaviour of the source spectrum. The spectral energy distribution of mid-March 2008 is modelled with a homogeneous one-zone synchrotron self Compton emission plus contributions from inverse Compton scattering of external photons from both the accretion disc and the broad line region. Indeed, some features in the optical-UV spectrum seem to indicate the presence of Seyfert-like components, such as the little blue bump and the big blue bump., 10 pages, 4 figures and 2 tables, accepted for publication in A&A

Published
2009

353. THE JUNE 2008 FLARE OF MARKARIAN 421 FROM OPTICAL TO TeV ENERGIES

Author

I. Donnarumma, V. Vittorini, S. Vercellone, E. Del Monte, M. Feroci, F. D'Ammando, L. Pacciani, A. W. Chen, M. Tavani, A. Bulgarelli, A. Giuliani, F. Longo, G. Pucella, A. Argan, G. Barbiellini, F. Boffelli, P. Caraveo, P. W. Cattaneo, V. Cocco, E. Costa, G. De Paris, G. Di Cocco, Y. Evangelista, M. Fiorini, T. Froysland, M. Frutti, F. Fuschino, M. Galli, F. Gianotti, C. Labanti, I. Lapshov, F. Lazzarotto, P. Lipari, M. Marisaldi, M. Mastropietro, S. Mereghetti, E. Morelli, A. Morselli, A. Pellizzoni, F. Perotti, P. Picozza, G. Porrovecchio, M. Prest, M. Rapisarda, A. Rappoldi, A. Rubini, P. Soffitta, M. Trifoglio, A. Trois, E. Vallazza, A. Zambra, D. Zanello, C. Pittori, P. Santolamazza, F. Verrecchia, P. Giommi, S. Colafrancesco, L. Salotti, M. Villata, C. M. Raiteri, W. P. Chen, N. V. Efimova, B. Jordan, T. S. Konstantinova, E. Koptelova, O. M. Kurtanidze, V. M. Larionov, J. A. Ros, A. C. Sadun, H. Anderhub, L. A. Antonelli, P. Antoranz, M. Backes, C. Baixeras, S. Balestra, J. A. Barrio, H. Bartko, D. Bastieri, J. Becerra González, J. K. Becker, W. Bednarek, K. Berger, E. Bernardini, A. Biland, R. K. Bock, G. Bonnoli, P. Bordas, D. Borla Tridon, V. Bosch-Ramon, T. Bretz, I. Britvitch, M. Camara, E. Carmona, A. Chilingarian, S. Commichau, J. L. Contreras, J. Cortina, M. T. Costado, S. Covino, V. Curtef, F. Dazzi, A. De Angelis, E. De Cea del Pozo, R. de los Reyes, B. De Lotto, M. De Maria, F. De Sabata, C. Delgado Mendez, A. Dominguez, D. Dorner, M. Doro, D. Elsaesser, M. Errando, D. Ferenc, E. Fernández, R. Firpo, M. V. Fonseca, L. Font, N. Galante, R. J. García López, M. Garczarczyk, M. Gaug, F. Goebel, D. Hadasch, M. Hayashida, A. Herrero, D. Höhne-Mönch, J. Hose, C. C. Hsu, S. Huber, T. Jogler, D. Kranich, A. La Barbera, A. Laille, E. Leonardo, E. Lindfors, S. Lombardi, M. López, E. Lorenz, P. Majumdar, G. Maneva, N. Mankuzhiyil, K. Mannheim, L. Maraschi, M. Mariotti, M. Martínez, D. Mazin, M. Meucci, M. Meyer, J. M. Miranda, R. Mirzoyan, J. Moldón, M. Moles, A. Moralejo, D. Nieto, K. Nilsson, J. Ninkovic, I. Oya, R. Paoletti, J. M. Paredes, M. Pasanen, D. Pascoli, F. Pauss, R. G. Pegna, M. A. Perez-Torres, M. Persic, L. Peruzzo, F. Prada, E. Prandini, N. Puchades, A. Raymers, W. Rhode, M. Ribó, J. Rico, M. Rissi, A. Robert, S. Rügamer, A. Saggion, T. Y. Saito, M. Salvati, M. Sanchez-Conde, P. Sartori, K. Satalecka, V. Scalzotto, V. Scapin, T. Schweizer, M. Shayduk, K. Shinozaki, S. N. Shore, N. Sidro, A. Sierpowska-Bartosik, A. Sillanpää, J. Sitarek, D. Sobczynska, F. Spanier, A. Stamerra, L. S. Stark, L. Takalo, F. Tavecchio, P. Temnikov, D. Tescaro, M. Teshima, M. Tluczykont, D. F. Torres, N. Turini, H. Vankov, A. Venturini, V. Vitale, R. M. Wagner, W. Wittek, V. Zabalza, F. Zandanel, R. Zanin, J. Zapatero, V. Acciari, E. Aliu, T. Arlen, M. Beilicke, W. Benbow, S. M. Bradbury, J. H. Buckley, V. Bugaev, Y. Butt, K. Byrum, A. Cannon, A. Cesarini, Y. C. Chow, L. Ciupik, P. Cogan, P. Colin, W. Cui, M. K. Daniel, R. Dickherber, C. Duke, T. Ergin, S. J. Fegan, J. P. Finley, G. Finnegan, P. Fortin, A. Furniss, D. Gall, G. H. Gillanders, R. Guenette, G. Gyuk, J. Grube, D. Hanna, J. Holder, D. Horan, C. M. Hui, T. Brian Humensky, A. Imran, P. Kaaret, N. Karlsson, M. Kertzman, D. Kieda, J. Kildea, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, G. Maier, A. McCann, M. McCutcheon, A. Milovanovic, P. Moriarty, T. Nagai, R. A. Ong, A. N. Otte, D. Pandel, J. S. Perkins, A. Pichel, M. Pohl, K. Ragan, L. C. Reyes, P. T. Reynolds, E. Roache, H. J. Rose, M. Schroedter, G. H. Sembroski, A. W. Smith, D. Steele, S. P. Swordy, M. Theiling, J. A. Toner, L. Valcarcel, A. Varlotta, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, D. A. Williams, S. Wissel, M. Wood, B. Zitzer, I., Donnarumma, V., Vittorini, S., Vercellone, E. D., Monte, M., Feroci, F., D'Ammando, L., Pacciani, A. W., Chen, M., Tavani, A., Bulgarelli, A., Giuliani, Longo, Francesco, G., Pucella, A., Argan, G., Barbiellini, F., Boffelli, P., Caraveo, P. W., Cattaneo, V., Cocco, E., Costa, G. D., Pari, G. D., Cocco, Y., Evangelista, M., Fiorini, T., Froysland, M., Frutti, F., Fuschino, M., Galli, F., Gianotti, C., Labanti, I., Lapshov, F., Lazzarotto, P., Lipari, M., Marisaldi, M., Mastropietro, S., Mereghetti, E., Morelli, A., Morselli, A., Pellizzoni, F., Perotti, P., Picozza, G., Porrovecchio, M., Prest, M., Rapisarda, A., Rappoldi, A., Rubini, P., Soffitta, M., Trifoglio, A., Troi, E., Vallazza, A., Zambra, D., Zanello, C., Pittori, P., Santolamazza, F., Verrecchia, P., Giommi, S., Colafrancesco, L., Salotti, M., Villata, C. M., Raiteri, W. P., Chen, N. V., Efimova, B., Jordan, T. S., Konstantinova, E., Koptelova, O. M., Kurtanidze, V. M., Larionov, J. A., Ro, A. C., Sadun, H., Anderhub, L. A., Antonelli, P., Antoranz, M., Backe, C., Baixera, S., Balestra, J. A., Barrio, H., Bartko, D., Bastieri, J. B., Gonzalez, J. K., Becker, W., Bednarek, K., Berger, E., Bernardini, A., Biland, R. K., Bock, G., Bonnoli, P., Borda, D. B., Tridon, V., Bosch Ramon, T., Bretz, I., Britvitch, M., Camara, E., Carmona, A., Chilingarian, S., Commichau, J. L., Contrera, J., Cortina, M. T., Costado, S., Covino, V., Curtef, F., Dazzi, A. D., Angeli, E. D., Del Pozo, R. D., Reye, B. D., Lotto, M. D., Maria, F. D., Sabata, C. D., Mendez, A., Dominguez, D., Dorner, M., Doro, D., Elsaesser, M., Errando, D., Ferenc, E., Fernandez, R., Firpo, M. V., Fonseca, L., Font, N., Galante, R. J. G., Lopez, M., Garczarczyk, M., Gaug, F., Goebel, D., Hadasch, M., Hayashida, A., Herrero, D., Hohne Monch, J., Hose, C. C., Hsu, S., Huber, T., Jogler, D., Kranich, A. L., Barbera, A., Laille, E., Leonardo, E., Lindfor, S., Lombardi, M., Lopez, E., Lorenz, P., Majumdar, G., Maneva, N., Mankuzhiyil, K., Mannheim, L., Maraschi, M., Mariotti, M., Martinez, D., Mazin, M., Meucci, M., Meyer, J. M., Miranda, R., Mirzoyan, J., Moldon, M., Mole, A., Moralejo, D., Nieto, K., Nilsson, J., Ninkovic, I., Oya, R., Paoletti, J. M., Parede, M., Pasanen, D., Pascoli, F., Pau, R. G., Pegna, M. A., Perez Torre, M., Persic, L., Peruzzo, F., Prada, E., Prandini, N., Puchade, A., Raymer, W., Rhode, M., Ribo, J., Rico, M., Rissi, A., Robert, S., Rugamer, A., Saggion, T. Y., Saito, M., Salvati, M., Sanchez Conde, P., Sartori, K., Satalecka, V., Scalzotto, V., Scapin, T., Schweizer, M., Shayduk, K., Shinozaki, S. N., Shore, N., Sidro, A., Sierpowska Bartosik, A., Sillanpaa, J., Sitarek, D., Sobczynska, F., Spanier, A., Stamerra, L. S., Stark, L., Takalo, F., Tavecchio, P., Temnikov, D., Tescaro, M., Teshima, M., Tluczykont, D. F., Torre, N., Turini, H., Vankov, A., Venturini, V., Vitale, R. M., Wagner, W., Wittek, V., Zabalza, F., Zandanel, R., Zanin, J., Zapatero, V., Acciari, E., Aliu, T., Arlen, M., Beilicke, W., Benbow, S. M., Bradbury, J. H., Buckley, V., Bugaev, Y., Butt, K., Byrum, A., Cannon, A., Cesarini, Y. C., Chow, L., Ciupik, P., Cogan, P., Colin, W., Cui, M. K., Daniel, R., Dickherber, C., Duke, T., Ergin, S. J., Fegan, J. P., Finley, G., Finnegan, P., Fortin, A., Furni, D., Gall, G. H., Gillander, R., Guenette, G., Gyuk, J., Grube, D., Hanna, J., Holder, D., Horan, C. M., Hui, T. B., Humensky, A., Imran, P., Kaaret, N., Karlsson, M., Kertzman, D., Kieda, J., Kildea, A., Konopelko, H., Krawczynski, F., Krennrich, M. J., Lang, S., Lebohec, G., Maier, A., Mccann, M., Mccutcheon, A., Milovanovic, P., Moriarty, T., Nagai, R. A., Ong, A. N., Otte, D., Pandel, J. S., Perkin, A., Pichel, M., Pohl, K., Ragan, L. C., Reye, P. T., Reynold, E., Roache, H. J., Rose, M., Schroedter, G. H., Sembroski, A. W., Smith, D., Steele, S. P., Swordy, M., Theiling, J. A., Toner, L., Valcarcel, A., Varlotta, S. P., Wakely, J. E., Ward, T. C., Weeke, A., Weinstein, D. A., William, S., Wissel, M., Wood, B., Zitzer, Donnarumma I, Vittorini V, Vercellone S, del Monte E, Feroci M, DAmmando F, Pacciani L, Chen A W, Tavani M, Bulgarelli A, Giuliani A, Longo F, Pucella G, Argan A, Barbiellini G, Boffelli F, Caraveo P, Cattaneo P W, Cocco V, Costa E, DeParis G, Di Cocco G, Evangelista Y, Fiorini M, Froysland T, Frutti M, Fuschino F, Galli M, Gianotti F, Labanti C, Lapshov I, Lazzarotto F, Lipari P, Marisaldi M, Mastropietro M, Mereghetti S, Morelli E, Morselli A, Pellizzoni A, Perotti F, Picozza P, Porrovecchio G, Prest M, Rapisarda M, Rappoldi A, Rubini A, Soffitta P, Trifoglio M, Trois A, Vallazza E, Zambra A, Zanello D, Pittori C, Santolamazza P, Verrecchia F, Giommi P, Colafrancesco S, Salotti L, Villata M, Raiteri C M, Chen W P, Efimova N V, Jordan B, Konstantinova T S, Koptelova E, Kurtanidze O M, Larionov V M, Ros J A, Sadun A C, Anderhub H, Antonelli L A, Antoranz P, Backes M, Baixeras C, Balestra S, Barrio J A, Bartko H, Bastieri D, González J Becerra, Becker J K, Bednarek W, Berger K, Bernardini E, Biland A, Bock R K, Bonnoli G, Bordas P, Tridon D Borla, Bosch-Ramon V, Bretz T, Britvitch I, Camara M, Carmona E, Chilingarian A, Commichau S, Contreras J L, Cortina J, Costado M T, Covino S, Curtef V, Dazzi F, DeAngelis A, DeCea del Pozo E, de los Reyes R, DeLotto B, DeMaria M, DeSabata F, Mendez C Delgado, Dominguez A, Dorner D, Doro M, Elsaesser D, Errando M, Ferenc D, Fernández E, Firpo R, Fonseca M V, Font L, Galante N, García López R J, Garczarczyk M, Gaug M, Goebel F, Hadasch D, Hayashida M, Herrero A, Höhne-Mönch D, Hose J, Hsu C C, Huber S, Jogler T, Kranich D, La Barbera A, Laille A, Leonardo E, Lindfors E, Lombardi S, López M, Lorenz E, Majumdar P, Maneva G, Mankuzhiyil N, Mannheim K, Maraschi L, Mariotti M, Martínez M, Mazin D, Meucci M, Meyer M, Miranda J M, Mirzoyan R, Moldón J, Moles M, Moralejo A, Nieto D, Nilsson K, Ninkovic J, Oya I, Paoletti R, Paredes J M, Pasanen M, Pascoli D, Pauss F, Pegna R G, Perez-Torres M A, Persic M, Peruzzo L, Prada F, Prandini E, Puchades N, Raymers A, Rhode W, Ribó M, Rico J, Rissi M, Robert A, Rügamer S, Saggion A, Saito T Y, Salvati M, Sanchez-Conde M, Sartori P, Satalecka K, Scalzotto V, Scapin V, Schweizer T, Shayduk M, Shinozaki K, Shore S N, Sidro N, Sierpowska-Bartosik A, Sillanpää A, Sitarek J, Sobczynska D, Spanier F, Stamerra A, Stark L S, Takalo L, Tavecchio F, Temnikov P, Tescaro D, Teshima M, Tluczykont M, Torres D F, Turini N, Vankov H, Venturini A, Vitale V, Wagner R M, Wittek W, Zabalza V, Zandanel F, Zanin R, Zapatero J, Acciari V, Aliu E, Arlen T, Beilicke M, Benbow W, Bradbury S M, Buckley J H, Bugaev V, Butt Y, Byrum K, Cannon A, Cesarini A, Chow Y C, Ciupik L, Cogan P, Colin P, Cui W, Daniel M K, Dickherber R, Duke C, Ergin T, Fegan S J, Finley J P, Finnegan G, Fortin P, Furniss A, Gall D, Gillanders G H, Guenette R, Gyuk G, Grube J, Hanna D, Holder J, Horan D, Hui C M, Humensky T Brian, Imran A, Kaaret P, Karlsson N, Kertzman M, Kieda D, Kildea J, Konopelko A, Krawczynski H, Krennrich F, Lang M J, LeBohec S, Maier G, McCann A, McCutcheon M, Milovanovic A, Moriarty P, Nagai T, Ong R A, Otte A N, Pandel D, Perkins J S, Pichel A, Pohl M, Ragan K, Reyes L C, Reynolds P T, Roache E, Rose H J, Schroedter M, Sembroski G H, Smith A W, Steele D, Swordy S P, Theiling M, Toner J A, Valcarcel L, Varlotta A, Wakely S P, Ward J E, Weekes T C, Weinstein A, Williams D A, Wissel S, Wood M, and Zitzer B

Subjects
campaign, Raigs còsmics, BL Lacertae: individual: Mrk421, galaxies: jets, X-Rays: Galaxies, gamma rays: observations, radiation mechanisms: nonthermal, bl-lacertae objects, blazars, Flux, Astrophysics, 01 natural sciences, 7. Clean energy, High Energy Gamma-ray Astronomy, law.invention, Raigs gamma, law, optical, MAGIC (telescope), Agile, blazr, X-ray, gamma, high energy observation, 010303 astronomy & astrophysics, webt, Physics, x-ray-spectra, Astrophysics (astro-ph), gamma-rays, lac objects, xmm-newton, Spectral energy distribution, Electrónica, Física nuclear, Raigs X, Electricidad, Flare, outburst, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, 0103 physical sciences, X-rays, BL Lacertae objects: individual (Mrk 421) – gamma rays: observations – galaxies: jets – radiation mechanisms: non-thermal – X-rays: galaxies, Blazar, Cosmic rays, 010308 nuclear & particles physics, Gamma rays, Astronomy and Astrophysics, Active Galactic Nuclei, radiation mechanisms: non-thermal, Light curve, Galaxies, Galàxies, MAGIC telescope, Space and Planetary Science, Very High Energy Gamma-ray Astronomy, ddc:520, AGILE satellite, bl lacertae objects: individual (mrk 421), Energy (signal processing), Lepton
Abstract

We present optical, X-ray, high energy ($\lessapprox 30$ GeV) and very high energy ($\gtrapprox 100$ GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high energy $\gamma$-ray signal was detected by AGILE with \sqrt{TS}=4.5 on June 9--15, with $F(E>100 \mathrm{MeV})= 42^{+14}_{-12}\times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. This flaring state is brighter than the average flux observed by EGRET by a factor of $\sim$3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a 5-day flare (June 9-15) peaking at $\sim$ 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A Swift/XRT observation near the flaring maximum revealed the highest 2-10 keV flux ever observed from this source, of 2.6 $\times 10^{-9}$ erg cm$^{-2}$ s$^{-1}$ (i.e. > 100 mCrab). A peak synchrotron energy of $\sim$3 keV was derived, higher than typical values of $\sim$0.5-1 keV. VHE observations with MAGIC and VERITAS on June 6-8 show the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a twelve-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The $\gamma$-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet., Comment: accepted for publication in ApJL, 7 pages, 2 figures, 1 table

Published
2009

354. Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae.

Author

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, and Chatterjee R

Abstract

Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales 1-3 . 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 rare 4 in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet 5 , plasma instabilities 6,7 or orbital motion in an accretion disc 7,8 . 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 blazars 10 , is powered by a 1.7 × 10 8  M Sun (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 instabilities 6 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., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2022
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355. Blazar spectral variability as explained by a twisted inhomogeneous jet.

Author

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, and Vince O

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.

Published
2017
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356. The inner jet of an active galactic nucleus as revealed by a radio-to-gamma-ray outburst.

Author

Marscher AP, Jorstad SG, D'Arcangelo FD, Smith PS, Williams GG, Larionov VM, Oh H, Olmstead AR, Aller MF, Aller HD, McHardy IM, Lähteenmäki A, Tornikoski M, Valtaoja E, Hagen-Thorn VA, Kopatskaya EN, Gear WK, Tosti G, Kurtanidze O, Nikolashvili M, Sigua L, Miller HR, and Ryle WT

Abstract

Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV gamma-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images.

Published
2008
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