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Published May 2023 | public
Journal Article

Simultaneous space and phase resolved X-ray polarimetry of the Crab pulsar and nebula

Bucciantini, Niccoló ORCID icon
Ferrazzoli, Riccardo ORCID icon
Bachetti, Matteo ORCID icon
Rankin, John ORCID icon
Di Lalla, Niccoló ORCID icon
Sgró, Carmelo ORCID icon
Omodei, Nicola ORCID icon
Kitaguchi, Takao
Mizuno, Tsunefumi ORCID icon
Gunji, Shuichi ORCID icon
Watanabe, Eri ORCID icon
Baldini, Luca ORCID icon
Slane, Patrick O. ORCID icon
Weisskopf, Martin C. ORCID icon
Romani, Roger W. ORCID icon
Possenti, Andrea ORCID icon
Marshall, Herman L. ORCID icon
Silvestri, Stefano ORCID icon
Pacciani, Luigi ORCID icon
Negro, Michela ORCID icon
Muleri, Fabio ORCID icon
de Oña Wilhelmi, Emma ORCID icon
Xie, Fei ORCID icon
Heyl, Jeremy ORCID icon
Pesce-Rollins, Melissa ORCID icon
Wong, Josephine ORCID icon
Pilia, Maura ORCID icon
Agudo, Ivan ORCID icon
Antonelli, Lucio A. ORCID icon
Baumgartner, Wayne H. ORCID icon
Bellazzini, Ronaldo ORCID icon
Bianchi, Stefano ORCID icon
Bongiorno, Stephen D. ORCID icon
Bonino, Raffaella ORCID icon
Brez, Alessandro ORCID icon
Capitanio, Fiamma ORCID icon
Castellano, Simone ORCID icon
Cavazzuti, Elisabetta ORCID icon
Chen, Chien-Ting J. ORCID icon
Ciprini, Stefano ORCID icon
Costa, Enrico ORCID icon
De Rosa, Alessandra ORCID icon
Del Monte, Ettore ORCID icon
Di Gesu, Laura ORCID icon
Di Marco, Alessandro ORCID icon
Donnarumma, Immacolata ORCID icon
Doroshenko, Victor ORCID icon
Dovciak, Michal ORCID icon
Ehlert, Steven R. ORCID icon
Enoto, Teruaki ORCID icon
Evangelista, Yuri ORCID icon
Fabiani, Sergio ORCID icon
García, Javier A. ORCID icon
Hayashida, Kiyoshi
Iwakiri, Wataru B. ORCID icon
Jorstad, Svetlana G. ORCID icon
Kaaret, Philip E. ORCID icon
Karas, Vladimir ORCID icon
Kislat, Fabian ORCID icon
Kolodziejczak, Jeffery J. ORCID icon
Krawczynski, Henric ORCID icon
La Monaca, Fabio ORCID icon
Latronico, Luca ORCID icon
Liodakis, Ioannis ORCID icon
Maldera, Simone ORCID icon
Manfreda, Alberto ORCID icon
Marin, Frédéric ORCID icon
Marinucci, Andrea ORCID icon
Marscher, Alan P. ORCID icon
Massaro, Francesco ORCID icon
Matt, Giorgio ORCID icon
Mitsuishi, Ikuyuki
Ng, C.-Y. ORCID icon
O'Dell, Stephen L. ORCID icon
Oppedisano, Chiara ORCID icon
Papitto, Alessandro ORCID icon
Pavlov, George G. ORCID icon
Peirson, Abel L. ORCID icon
Perri, Matteo ORCID icon
Petrucci, Pierre-Olivier ORCID icon
Poutanen, Juri ORCID icon
Puccetti, Simonetta ORCID icon
Ramsey, Brian D. ORCID icon
Ratheesh, Ajay ORCID icon
Roberts, Oliver J. ORCID icon
Soffitta, Paolo ORCID icon
Spandre, Gloria ORCID icon
Swartz, Doug ORCID icon
Tamagawa, Toru ORCID icon
Tavecchio, Fabrizio ORCID icon
Taverna, Roberto ORCID icon
Tawara, Yuzuru
Tennant, Allyn F. ORCID icon
Thomas, Nicolas E.
Tombesi, Francesco ORCID icon
Trois, Alessio ORCID icon
Tsygankov, Sergey S. ORCID icon
Turolla, Roberto ORCID icon
Vink, Jacco ORCID icon
Wu, Kinwah ORCID icon
Zane, Silvia ORCID icon


The Crab pulsar and its nebula are among the most studied astrophysical systems, and constitute one of the most promising environments where high-energy processes and particle acceleration can be investigated. They are the only objects for which significant X-ray polarization was detected in the past. Here we present the Imaging X-ray Polarimetry Explorer (IXPE) observation of the Crab pulsar and nebula. The total pulsar pulsed emission in the [2–8] keV energy range is unpolarized. Significant polarization up to 15% is detected in the core of the main peak. The nebula has a total space integrated polarized degree of 20% and polarization angle of 145°. The polarized maps show a large variation in the local polarization, and regions with a polarized degree up to 45–50%. The polarization pattern suggests a predominantly toroidal magnetic field. Our findings for the pulsar are inconsistent with most inner magnetospheric models, and suggest emission is more likely to come from the wind region. For the nebula, the polarization map suggests a patchy distribution of turbulence, uncorrelated with the intensity, in contrast with simple expectations from numerical models.

Additional Information

© The Author(s), under exclusive licence to Springer Nature Limited 2023. The IXPE is a joint US and Italian mission. The US contribution is supported by NASA and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract no. NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract no. ASI-OHBI-2017-12-I.0, agreement nos. ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreement nos. ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). The research at Boston University was supported in part by National Science Foundation grant no. AST-2108622. Part of the French contributions is supported by the Scientific Research National Center (CNRS) and the French spatial agency (CNES). I.A. acknowledges financial support from the Spanish 'Ministerio de Ciencia e Innovación' (grant no. MCIN/AEI/ 10.13039/501100011033) through the Center of Excellence Severo Ochoa award for the Instituto de Astrofísica de Andalucía-CSIC (grant no. CEX2021-001131-S), and through grant nos. PID2019-107847RB-C44 and PID2022-139117NB-C44. C.-Y.N. is supported by a GRF grant from the Hong Kong Government under no. HKU 17305419. N.B. was supported by the INAF MiniGrant 'PWNnumpol - Numerical Studies of Pulsar Wind Nebulae in The Light of IXPE'. J.H. acknowledges support from the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant, the Canadian Space Agency through the co-investigator grant programme, and computational resources and services provided by Compute Canada, Advanced Research Computing at the University of British Columbia, and the SciServer science platform. S.G. and E.W. were supported by grant nos. JSPS KAKENHI JP 19H00696 and 22K14068. Contributions. N.B. led the data analysis and the writing of the paper. R.F., M.B., J.R., L.P. and F.M. contributed to data analysis and data calibration. N.D.L., C.S., N.O., T.K., T.M., S.G. and E.W. contributed to data analysis and results interpretation. M.C.W., M.N., S.S., E.D.O.W., F.X., J.H., R.W.R., P.T., A.P. and H.L.M. contributed to text revision and data interpretation. L.B. and M.P.-R. contributed to software development. The remaining members of the IXPE collaboration contributed to the design of the mission, to the calibration of the instrument, to defining its science case and to the planning of the observations. All authors provided inputs and comments on the paper. Data availability. Data from the Crab PSR and nebula observation are available in the HEASARC IXPE Data Archive (https://heasarc.gsfc.nasa.gov/docs/ixpe/archive/). Additional data are available in the Supplementary Information and from figshare at https://doi.org/10.6084/m9.figshare.22203163. Source data are provided with this paper. Code availability. The ixpeobssim software and documentation can be downloaded at https://github.com/lucabaldini/ixpeobssim. Other information supporting the findings of this study, and specific data-reduction pipelines, are available from the corresponding author upon request. The authors declare no competing interests.

Additional details

August 22, 2023
October 20, 2023