Polarized x-rays from a magnetar
Roberto Taverna, R. Turolla, Fabio Muleri, Jeremy Heyl, Silvia Zane, L. Baldini, Denis González–Caniulef, Matteo Bachetti, John Rankin, Ilaria Caiazzo, Niccolò Di Lalla, Victor Doroshenko, M. Errando, Ephraim Gau, Demet Kırmızıbayrak, H. Krawczynski, Michela Negro, Mason Ng, N. Omodei, Andrea Possenti, Toru Tamagawa, Keisuke Uchiyama, Martin C. Weisskopf, I. Agudo, L. A. Antonelli, W. H. Baumgartner, R. Bellazzini, S. Bianchi, Stephen D. Bongiorno, R. Bonino, A. Brez, N. Bucciantini, Fiamma Capitanio, Simone Castellano, E. Cavazzuti, S. Ciprini, E. Costa, Alessandra De Rosa, E. Del Monte, Laura Di Gesu, Alessandro Di Marco, I. Donnarumma, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Y. Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. García, Shuichi Gunji, Kiyoshi Hayashida, W. Iwakiri, Svetlana G. Jorstad, V. Karas, Takao Kitaguchi, Jeffery J. Kolodziejczak, Fabio La Monaca, L. Latronico, Ioannis Liodakis, S. Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Alan P. Marscher, Herman L. Marshall, G. Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Stephen C. Y. Ng, Stephen L. O’Dell, C. Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, M. Perri, M. Pesce-Rollins, M. Pilia, Juri Poutanen, Simonetta Puccetti, Brian D. Ramsey, Ajay Ratheesh, Roger W. Romani, C. Sgró, Patrick Slane, P. Soffitta, G. Spandre, F. Tavecchio, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, A. Trois, Sergey S. Tsygankov, Jacco Vink, Kinwah Wu, Fei Xie
Abstract
Magnetars are neutron stars with ultrastrong magnetic fields, which can be observed in x-rays. Polarization measurements could provide information on their magnetic fields and surface properties. We observed polarized x-rays from the magnetar 4U 0142+61 using the Imaging X-ray Polarimetry Explorer and found a linear polarization degree of 13.5 ± 0.8% averaged over the 2- to 8-kilo-electron volt band. The polarization changes with energy: The degree is 15.0 ± 1.0% at 2 to 4 kilo-electron volts, drops below the instrumental sensitivity ~4 to 5 kilo-electron volts, and rises to 35.2 ± 7.1% at 5.5 to 8 kilo-electron volts. The polarization angle also changes by 90° at ~4 to 5 kilo-electron volts. These results are consistent with a model in which thermal radiation from the magnetar surface is reprocessed by scattering off charged particles in the magnetosphere.