@article{discovery10160826,
            year = {2022},
           month = {November},
          number = {7937},
          volume = {611},
            note = {Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.},
       publisher = {Springer Science and Business Media LLC},
           title = {Polarized blazar X-rays imply particle acceleration in shocks},
           pages = {677--681},
         journal = {Nature},
            issn = {0028-0836},
          author = {Liodakis, Ioannis and Marscher, Alan P and Agudo, Iv{\'a}n and Berdyugin, Andrei V and Bernardos, Maria I and Bonnoli, Giacomo and Borman, George A and Casadio, Carolina and Casanova, V{\i} Ctor and Cavazzuti, Elisabetta and Rodriguez Cavero, Nicole and Di Gesu, Laura and Di Lalla, Niccol{\'o} and Donnarumma, Immacolata and Ehlert, Steven R and Errando, Manel and Escudero, Juan and Garc{\i} A-Comas, Maya and Ag{\i} S-Gonz{\'a}lez, Beatriz and Husillos, C{\'e}sar and Jormanainen, Jenni and Jorstad, Svetlana G and Kagitani, Masato and Kopatskaya, Evgenia N and Kravtsov, Vadim and Krawczynski, Henric and Lindfors, Elina and Larionova, Elena G and Madejski, Grzegorz M and Marin, Fr{\'e}d{\'e}ric and Marchini, Alessandro and Marshall, Herman L and Morozova, Daria A and Massaro, Francesco and Masiero, Joseph R and Mawet, Dimitri and Middei, Riccardo and Millar-Blanchaer, Maxwell A and Myserlis, Ioannis and Negro, Michela and Nilsson, Kari and O'Dell, Stephen L and Omodei, Nicola and Pacciani, Luigi and Paggi, Alessandro and Panopoulou, Georgia V and Peirson, Abel L and Perri, Matteo and Petrucci, Pierre-Olivier and Poutanen, Juri and Puccetti, Simonetta and Romani, Roger W and Sakanoi, Takeshi and Savchenko, Sergey S and Sota, Alfredo and Tavecchio, Fabrizio and Tinyanont, Samaporn and Vasilyev, Andrey A and Weaver, Zachary R and Zhovtan, Alexey V and Antonelli, Lucio A and Bachetti, Matteo and Baldini, Luca and Baumgartner, Wayne H and Bellazzini, Ronaldo and Bianchi, Stefano and Bongiorno, Stephen D and Bonino, Raffaella and Brez, Alessandro and Bucciantini, Niccol{\'o} and Capitanio, Fiamma and Castellano, Simone and Ciprini, Stefano and Costa, Enrico and De Rosa, Alessandra and Del Monte, Ettore and Di Marco, Alessandro and Doroshenko, Victor and Dov{\vc}iak, Michal and Enoto, Teruaki and Evangelista, Yuri and Fabiani, Sergio and Ferrazzoli, Riccardo and Garcia, Javier A and Gunji, Shuichi and Hayashida, Kiyoshi and Heyl, Jeremy and Iwakiri, Wataru and Karas, Vladimir and Kitaguchi, Takao and Kolodziejczak, Jeffery J and La Monaca, Fabio and Latronico, Luca and Maldera, Simone and Manfreda, Alberto and Marinucci, Andrea and Matt, Giorgio and Mitsuishi, Ikuyuki and Mizuno, Tsunefumi and Muleri, Fabio and Ng, Stephen C-Y and Oppedisano, Chiara and Papitto, Alessandro and Pavlov, George G and Pesce-Rollins, Melissa and Pilia, Maura and Possenti, Andrea and Ramsey, Brian D and Rankin, John and Ratheesh, Ajay and Sgr{\'o}, Carmelo and Slane, Patrick and Soffitta, Paolo and Spandre, Gloria and Tamagawa, Toru and Taverna, Roberto and Tawara, Yuzuru and Tennant, Allyn F and Thomas, Nicolas E and Tombesi, Francesco and Trois, Alessio and Tsygankov, Sergey and Turolla, Roberto and Vink, Jacco and Weisskopf, Martin C and Wu, Kinwah and Xie, Fei and Zane, Silvia},
             url = {https://doi.org/10.1038/s41586-022-05338-0},
        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 {\ensuremath{\Pi}}X 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.},
        keywords = {X-Rays, Radiography, Acceleration, Aircraft, Cell Nucleus}
}