Paper

Polarized Blazar X-rays imply particle acceleration in shocks

Poutanen, Juri, Ettore Del Monte, Kitaguchi, Takao, Savchenko, Sergey S, Papitto, Alessandro, Enoto, Teruaki, Oppedisano, Chiara, Pavlov, George G, Latronico, Luca, Fabiani, Sergio, Tsygankov, Sergey, Wu, Kinwah, Cavazzuti, Elisabetta, Heyl, Jeremy, García-Comas, Maya, Larionova, Elena G, Baumgartner, Wayne H, Petrucci, Pierre-Olivier, Borman, George A, Mitsuishi, Ikuyuki, Tennant, Allyn F, Xie, Fei, Marshall, Herman L, Alessandro Di Marco, Weisskopf, Martin C, Giorgio, Matt, Madejski, Grzegorz M, Liodakis, Ioannis, Muleri, Fabio, Pacciani, Luigi, Myserlis, Ioannis, Kagitani, Masato, Tavecchio, Fabrizio, Sakanoi, Takeshi, Ferrazzoli, Riccardo, Berdyugin, Andrei V, Sota, Alfredo, Tamagawa, Toru, Agís-González, Beatriz, Lindfors, Elina, Perri, Matteo, Masiero, Joseph R, Pilia, Maura, O'Dell, Stephen L, Jormanainen, Jenni, Krawczynski, Henric, Millar-Blanchaer, Maxwell A, Bernardos, Maria I, Baldini, Luca, Pesce-Rollins, Melissa, Turolla, Roberto, Evangelista, Yuri, Marin, Frédéric, Fabio La Monaca, Puccetti, Simonetta, Romani, Roger W, Vink, Jacco, Costa, Enrico, Husillos, César, Ciprini, Stefano, Nicole

2023

Overview

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 \\(\\sim 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 earlier (Jorstad et al., 2005; Marin et al., 2018; Blinov et al., 2021), 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 \\(\\Pi_X \\sim10\\%\\), a factor of \\(\\sim2\\) 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.

• Publisher: Cornell University Library, arXiv.org
• Subject: Active galactic nuclei / Blazars / Deposition / Emission / Energetic particles / Gamma rays / High energy astronomy / LF radio / Linear polarization / Particle acceleration / Radio jets (astronomy) / Relativistic effects / Relativistic plasmas / Supermassive black holes / X ray imagery / X-ray astronomy / X-rays