X-Ray Polarization of the Eastern Lobe of SS 433
P. Kaaret, Riccardo Ferrazzoli, Stefano Silvestri, Michela Negro, Alberto Manfreda, Kinwah Wu, E. Costa, P. Soffitta, Samar Safí-Harb, Juri Poutanen, Alexandra Veledina, Alessandro Di Marco, Patrick Slane, S. Bianchi, Adam Ingram, Roger W. Romani, Nicolò Cibrario, Brydyn Mac Intyre, Romana Mikušincová, Ajay Ratheesh, James F. Steiner, Jiří Svoboda, Stefano Tugliani, I. Agudo, L. A. Antonelli, Matteo Bachetti, L. Baldini, W. H. Baumgartner, R. Bellazzini, Stephen D. Bongiorno, R. Bonino, A. Brez, N. Bucciantini, Fiamma Capitanio, Simone Castellano, E. Cavazzuti, Chien‐Ting Chen, S. Ciprini, Alessandra De Rosa, E. Del Monte, Laura Di Gesu, Niccolò Di Lalla, I. Donnarumma, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Y. Evangelista, Sergio Fabiani, Javier A. García, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, W. Iwakiri, Svetlana G. Jorstad, V. Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, H. Krawczynski, Fabio La Monaca, L. Latronico, Ioannis Liodakis, S. Maldera, Frédéric Marin, Andrea Marinucci, Alan P. Marscher, Herman L. Marshall, F. Massaro, G. Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Fabio Muleri, C.‐Y. Ng, Stephen L. O’Dell, N. Omodei, C. Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, M. Perri, M. Pesce-Rollins, Pierre-Olivier Petrucci, M. Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, John Rankin, O. J. Roberts, C. Sgró, G. Spandre, Douglas A. Swartz, Toru Tamagawa, F. Tavecchio, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, A. Trois
Abstract
Abstract How astrophysical systems translate the kinetic energy of bulk motion into the acceleration of particles to very high energies is a pressing question. SS 433 is a microquasar that emits TeV γ -rays indicating the presence of high-energy particles. A region of hard X-ray emission in the eastern lobe of SS 433 was recently identified as an acceleration site. We observed this region with the Imaging X-ray Polarimetry Explorer and measured a polarization degree in the range 38%–77%. The high polarization degree indicates the magnetic field has a well-ordered component if the X-rays are due to synchrotron emission. The polarization angle is in the range −12° to +10° (east of north), which indicates that the magnetic field is parallel to the jet. Magnetic fields parallel to the bulk flow have also been found in supernova remnants and the jets of powerful radio galaxies. This may be caused by interaction of the flow with the ambient medium.