Polarized x-rays from a magnetar

Full list of authors: Taverna, Roberto; Turolla, Roberto; Muleri, Fabio; Heyl, Jeremy; Zane, Silvia; Baldini, Luca; Gonzalez-Caniulef, Denis; Bachetti, Matteo; Rankin, John; Caiazzo, Ilaria; Di Lalla, Niccolo; Doroshenko, Victor; Errando, Manel; Gau, Ephraim; Kirmizibayrak, Demet; Krawczynski, Henric; Negro, Michela; Ng, Mason; Omodei, Nicola; Possenti, Andrea; Tamagawa, Toru; Uchiyama, Keisuke; Weisskopf, Martin C.; Agudo, Ivan; Antonelli, Lucio A.; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolo; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Ciprini, Stefano; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Marco, Alessandro; Donnarumma, Immacolata; Doviak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; La Monaca, Fabio; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Frederic; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Matt, Giorgio; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Ng, Stephen C-Y; O'Dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Pilia, Maura; Poutanen, Juri; Puccetti, Simonetta; Ramsey, Brian D.; Ratheesh, Ajay; Romani, Roger W.; Sgro, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Tavecchio, Fabrizio; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicolas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey; Vink, Jacco; Wu, Kinwah; Xie, Fei.
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. © 2022 The Authors.
R.Ta. and R.Tu. acknowledge financial support from the Italian MUR through grant PRIN 2017LJ39LM. J.H., D.G.-C., I.C., and D.K. acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number 5007110, and the Canadian Space Agency. D.G.-C. is a Canadian Institute for Theoretical Astrophysical (CITA) National Fellow (grant no. CITA 490888-16). E.G. and H.K. acknowledge NASA support under grants 80NSSC18K0264, 80NSSC22K1291, 80NSSC21K1817, and NNX16AC24G. M.Ne. acknowledges support from NASA under award 80GSFC21M0002. T.T. was supported by grant JSPS KAKENHI JP19H05609. F.Mu., J.R., S.B., E.Co., E.D.M., A.D.M., Y.E., S.F., R.F., F.L.M., G.M., M.Pe., A.R., P.So., and A.T. were supported by ASI and INAF under grants ASI-INAF-2017-12-H0 and ASI-INAF-2022-14-HH.0. L.B., L.L., R.Be., R.Bo., A.B., S.Ca., S.M., A.Mar., C.O., M.P.-R., C.S., and G.S. were supported by ASI and INFN under grants ASI-INFN-2017.13-H0 and ASI-INFN-2021-43-HH.0.
With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.