Abstract
The magnetic-field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle Ψ. Here we report the discovery of a ΨX rotation in the X-ray band in the blazar Markarian 421 at an average flux state. Across the 5 days of Imaging X-ray Polarimetry Explorer observations on 4–6 and 7–9 June 2022, ΨX rotated in total by ≥360°. Over the two respective date ranges, we find constant, within uncertainties, rotation rates (80 ± 9° per day and 91 ± 8° per day) and polarization degrees (ΠX = 10% ± 1%). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray-emitting site does not completely overlap the radio, infrared and optical emission sites, as no similar rotation of Ψ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region probably lies in a sheath surrounding an inner spine where the X-ray radiation is released.
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Data availability
The data that support the findings of this study are either publicly available at the HEASARC database or available from the corresponding author upon request.
Code availability
The ixpeobssim software and documentation can be downloaded at https://github.com/lucabaldini/ixpeobssim.
References
Blandford, R., Meier, D. & Readhead, A. Relativistic jets from active galactic nuclei. Annu. Rev. Astron. Astrophys. 57, 467–509 (2019).
Romero, G. E., Boettcher, M., Markoff, S. & Tavecchio, F. Relativistic jets in active galactic nuclei and microquasars. Space Sci. Rev. 207, 5–61 (2017).
Blandford, R. & Eichler, D. Particle acceleration at astrophysical shocks: a theory of cosmic ray origin. Phys. Rep. 154, 1–75 (1987).
Sironi, L. & Spitkovsky, A. Relativistic reconnection: an efficient source of non-thermal particles. Astrophys. J. Lett. 783, L21 (2014).
Bodo, G., Tavecchio, F. & Sironi, L. Kink-driven magnetic reconnection in relativistic jets: consequences for X-ray polarimetry of BL Lacs. Mon. Not. R. Astron. Soc. 501, 2836–2847 (2021).
Zhang, H. et al. Radiation and polarization signatures from magnetic reconnection in relativistic jets. I. A systematic study. Astrophys. J. 901, 149 (2020).
Comisso, L. & Sironi, L. Particle acceleration in relativistic plasma turbulence. Phys. Rev. Lett. 121, 255101 (2018).
Angel, J. R. P. & Stockman, H. S. Optical and infrared polarization of active extragalactic objects. Annu. Rev. Astron. Astrophys. 18, 321–361 (1980).
Blinov, D. et al. RoboPol: first season rotations of optical polarization plane in blazars. Mon. Not. R. Astron. Soc. 453, 1669–1683 (2015).
Blinov, D. et al. RoboPol: connection between optical polarization plane rotations and gamma-ray flares in blazars. Mon. Not. R. Astron. Soc. 474, 1296–1306 (2018).
Larionov, V. M. et al. The outburst of the blazar S5 0716+71 in 2011 October: shock in a helical jet. Astrophys. J. 768, 40 (2013).
Vlahakis, N. Disk–jet connection. In Blazar Variability Workshop II: Entering the GLAST Era, Astronomical Society of the Pacific Conference Series Vol. 350 (eds Miller, H. R. et al.) 169–177 (Astronomical Society of the Pacific, 2006).
Marscher, A. P. et al. The inner jet of an active galactic nucleus as revealed by a radio-to-γ-ray outburst. Nature 452, 966–969 (2008).
Marscher, A. P. et al. Probing the inner jet of the quasar PKS 1510−089 with multi-waveband monitoring during strong gamma-ray activity. Astrophys. J. Lett. 710, L126–L131 (2010).
Zhang, S. et al. Hard X-ray morphological and spectral studies of the galactic center molecular cloud Sgr B2: constraining past Sgr A* flaring activity. Astrophys. J. 815, 132 (2015).
Zhang, H., Deng, W., Li, H. & Böttcher, M. Polarization signatures of relativistic magnetohydrodynamic shocks in the blazar emission region. I. Force-free helical magnetic fields. Astrophys. J. 817, 63 (2016).
Hovatta, T. et al. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday rotation in parsec-scale AGN jets. Astron. J. 144, 105 (2012).
Gabuzda, D. C. Inherent and local magnetic field structures in jets from active galactic nuclei. Galaxies 9, 58 (2021).
Liodakis, I. et al. Two flares with one shock: the interesting case of 3C 454.3. Astrophys. J. 902, 61 (2020).
D’Arcangelo, F. D. et al. Rapid multiwaveband polarization variability in the quasar PKS 0420-014: optical emission from the compact radio jet. Astrophys. J. Lett. 659, L107–L110 (2007).
Peirson, A. L. & Romani, R. W. The polarization behavior of relativistic synchrotron jets. Astrophys. J. 864, 140 (2018).
Marscher, A. P. Turbulent, extreme multi-zone model for simulating flux and polarization variability in blazars. Astrophys. J. 780, 87 (2014).
Marscher, A. P. in Extragalactic Jets from Every Angle Vol. 313 (eds Massaro, F. et al.) 122–127 (Cambridge Univ. Press, 2015).
Marscher, A. P. & Jorstad, S. G. Frequency and time dependence of linear polarization in turbulent jets of blazars. Galaxies 9, 27 (2021).
Di Gesu, L. et al. Testing particle acceleration models for BL Lac jets with the Imaging X-ray Polarimetry Explorer. Astron. Astrophys. 662, A83 (2022).
Abdo, A. A. et al. Fermi Large Area Telescope observations of Markarian 421: the missing piece of its spectral energy distribution. Astrophys. J. 736, 131 (2011).
Lin, Y. C. et al. Detection of high-energy gamma-ray emission from the BL Lacertae object Markarian 421 by the EGRET Telescope on the Compton Observatory. Astrophys. J. Lett. 401, L61 (1992).
Punch, M. et al. Detection of TeV photons from the active galaxy Markarian 421. Nature 358, 477–478 (1992).
Giommi, P. et al. X-ray spectra, light curves and SEDs of blazars frequently observed by Swift. Mon. Not. R. Astron. Soc. 507, 5690–5702 (2021).
Middei, R. et al. The first hard X-ray spectral catalogue of blazars observed by NuSTAR. Mon. Not. R. Astron. Soc. 514, 3179–3190 (2022).
Donnarumma, I. et al. The June 2008 flare of Markarian 421 from optical to TeV energies. Astrophys. J. Lett. 691, L13–L19 (2009).
Di Gesu, L. et al. The X-ray polarization view of Mrk~421 in an average flux state as observed by the Imaging X-ray Polarimetry Explorer. Astrophys. J. Lett. https://doi.org/10.3847/2041-8213/ac913a (2022).
Liodakis, I. et al. Polarized blazar X-rays imply particle acceleration in shocks. Nature https://doi.org/10.1038/s41586-022-05338-0 (2022).
Marscher, A. P. et al. The inner jet of an active galactic nucleus as revealed by a radio-to-γ-ray outburst. Nature 452, 966–969 (2008).
Marscher, A. P. et al. Probing the inner jet of the quasar PKS 1510−089 with multi-waveband monitoring during strong gamma-ray activity. Astrophys. J. Lett. 710, L126–L131 (2010).
Blinov, D. et al. RoboPol: first season rotations of optical polarization plane in blazars. Mon. Not. R. Astron. Soc. 453, 1669–1683 (2015).
Blinov, D. et al. RoboPol: connection between optical polarization plane rotations and gamma-ray flares in blazars. Mon. Not. R. Astron. Soc. 474, 1296–1306 (2018).
Blinov, D. et al. RoboPol: AGN polarimetric monitoring data. Mon. Not. R. Astron. Soc. 501, 3715–3726 (2021).
Atwood, W. B. et al. The Large Area Telescope on the Fermi Gamma-Ray Space Telescope Mission. Astrophys. J. 697, 1071–1102 (2009).
Tavecchio, F. Probing magnetic fields and acceleration mechanisms in blazar jets with X-ray polarimetry. Galaxies 9, 37 (2021).
Kiehlmann, S. et al. The time-dependent distribution of optical polarization angle changes in blazars. Mon. Not. R. Astron. Soc. 507, 225–243 (2021).
MAGIC Collaboration et al. Multi-wavelength characterization of the blazar S5 0716+714 during an unprecedented outburst phase. Astron. Astrophys. 619, A45 (2018).
Hughes, P. A., Aller, H. D. & Aller, M. F. Polarized radio outbursts in BL Lacertae. II. The flux and polarization of a piston-driven shock. Astrophys. J. 298, 301–315 (1985).
Tavecchio, F., Landoni, M., Sironi, L. & Coppi, P. Probing shock acceleration in BL Lac jets through X-ray polarimetry: the time-dependent view. Mon. Not. R. Astron. Soc. 498, 599–608 (2020).
Kirk, J. G., Rieger, F. M. & Mastichiadis, A. Particle acceleration and synchrotron emission in blazar jets. Astron. Astrophys. 333, 452–458 (1998).
Georganopoulos, M. & Kazanas, D. Decelerating flows in TeV blazars: a resolution to the BL Lacertae-FR I unification problem. Astrophys. J. Lett. 594, L27–L30 (2003).
Ghisellini, G., Tavecchio, F. & Chiaberge, M. Structured jets in TeV BL Lac objects and radiogalaxies. Implications for the observed properties. Astron. Astrophys. 432, 401–410 (2005).
Chhotray, A. et al. On radiative acceleration in spine-sheath structured blazar jets. Mon. Not. R. Astron. Soc. 466, 3544–3557 (2017).
Giroletti, M., Giovannini, G., Taylor, G. B. & Falomo, R. A sample of low-redshift BL Lacertae objects. II. EVN and MERLIN data and multiwavelength analysis. Astrophys. J. 646, 801–814 (2006).
Piner, B. G., Pant, N. & Edwards, P. G. The jets of TeV blazars at higher resolution: 43 GHz and polarimetric VLBA observations from 2005 to 2009. Astrophys. J. 723, 1150–1167 (2010).
Marscher, A. P. & Jorstad, S. G. Linear polarization signatures of particle acceleration in high-synchrotron-peak blazars. Universe 8, 644 (2022).
Kiehlmann, S., Blinov, D., Pearson, T. J. & Liodakis, I. Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data. Mon. Not. R. Astron. Soc. 472, 3589–3604 (2017).
Kiehlmann, S. et al. Polarization angle swings in blazars: the case of 3C 279. Astron. Astrophys. 590, A10 (2016).
Bodo, G., Tavecchio, F. & Sironi, L. Kink-driven magnetic reconnection in relativistic jets: consequences for X-ray polarimetry of BL Lacs. Mon. Not. R. Astron. Soc. 501, 2836–2847 (2021).
Zhang, H., Li, X., Giannios, D. & Guo, F. First-principles prediction of X-ray polarization from magnetic reconnection in high-frequency BL Lacertae objects. Astrophys. J. 912, 129 (2021).
Zhang, H. et al. Radiation and polarization signatures from magnetic reconnection in relativistic jets. II. Connection with γ-rays. Astrophys. J. 924, 90 (2022).
Dong, L., Zhang, H. & Giannios, D. Kink instabilities in relativistic jets can drive quasi-periodic radiation signatures. Mon. Not. R. Astron. Soc. 494, 1817–1825 (2020).
Jorstad, S. G. et al. Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae. Nature 609, 265–268 (2022).
Peirson, A. L. & Romani, R. W. The polarization behavior of relativistic synchrotron jets. Astrophys. J. 864, 140 (2018).
Angelakis, E. et al. RoboPol: the optical polarization of gamma-ray-loud and gamma-ray-quiet blazars. Mon. Not. R. Astron. Soc. 463, 3365–3380 (2016).
Blinov, D. et al. RoboPol: do optical polarization rotations occur in all blazars? Mon. Not. R. Astron. Soc. 462, 1775–1785 (2016).
Rankin, J. et al. An algorithm to calibrate and correct the response to unpolarized radiation of the X-ray polarimeter onboard IXPE. Astron. J. 163, 39 (2022).
Ferrazzoli, R. et al. In-flight calibration system of imaging X-ray polarimetry explorer. J. Astron. Telesc. Instrum. Syst. 6, 048002 (2020).
Pesce-Rollins, M., Lalla, N. D., Omodei, N. & Baldini, L. An observation–simulation and analysis framework for the Imaging X-ray Polarimetry Explorer (IXPE). Nucl. Instrum. Methods Phys. Res. A 936, 224–226 (2019).
Baldini, L. et al. ixpeobssim: a simulation and analysis framework for the Imaging X-ray Polarimetry Explorer. SoftwareX https://doi.org/10.1016/j.softx.2022.101194 (2022).
Kislat, F., Clark, B., Beilicke, M. & Krawczynski, H. Analyzing the data from X-ray polarimeters with Stokes parameters. Astropart. Phys. 68, 45–51 (2015).
Soheila, A. et al. The Fermi-LAT Light Curve Repository. Astrophys. J. https://doi.org/10.3847/1538-4365/acbb6a (2023).
Arnaud, K., Dorman, B. & Gordon, C. XSPEC: an X-ray spectral fitting package. Astrophysics Source Code Library ascl:9910.005 (1999).
HI4PI Collaboration et al. HI4PI: A full-sky H i survey based on EBHIS and GASS. Astron. Astrophys. 594, A116 (2016).
Wilms, J., Allen, A. & McCray, R. On the absorption of X-rays in the interstellar medium. Astrophys. J. 542, 914–924 (2000).
Massaro, E., Perri, M., Giommi, P. & Nesci, R. Log-parabolic spectra and particle acceleration in the BL Lac object Mkn 421: spectral analysis of the complete BeppoSAX wide band X-ray data set. Astron. Astrophys. 413, 489–503 (2004).
Baloković, M. et al. Multiwavelength study of quiescent states of Mrk 421 with unprecedented hard X-ray coverage provided by NuSTAR in 2013. Astrophys. J. 819, 156 (2016).
Ramaprakash, A. N. et al. RoboPol: a four-channel optical imaging polarimeter. Mon. Not. R. Astron. Soc. 485, 2355–2366 (2019).
Kawabata, K. S. et al. A new spectropolarimeter at the Dodaira Observatory. Publ. Astron. Soc. Pac. 111, 898–908 (1999).
Akitaya, H. et al. HONIR: an optical and near-infrared simultaneous imager, spectrograph, and polarimeter for the 1.5-m Kanata telescope. In Ground-based and Airborne Instrumentation for Astronomy V, Society of Photo-Optical Instrumentation Engineers Conference Series Vol. 9147 (eds Ramsay, S. K. et al.) 91474O (SPIE, 2014).
Panopoulou, G. et al. Optical polarization map of the Polaris Flare with RoboPol. Mon. Not. R. Astron. Soc. 452, 715–726 (2015).
Hovatta, T. et al. Optical polarization of high-energy BL Lacertae objects. Astron. Astrophys. 596, A78 (2016).
Nilsson, K. et al. Long-term optical monitoring of TeV emitting blazars. I. Data analysis. Astron. Astrophys. 620, A185 (2018).
Nilsson, K. et al. Host galaxy subtraction of TeV candidate BL Lacertae objects. Astron. Astrophys. 475, 199–207 (2007).
Clemens, D. P., Pinnick, A. F. & Pavel, M. D. Polarimetric calibration of Mimir and the Galactic Plane Infrared Polarization Survey (GPIPS). Astrophys. J. Suppl. Ser. 200, 20 (2012).
Erwin, P. IMFIT: a fast, flexible new program for astronomical image fitting. Astrophys. J. 799, 226 (2015).
Moffat, A. F. J. A theoretical investigation of focal stellar images in the photographic emulsion and application to photographic photometry. Astron. Astrophys. 3, 455 (1969).
Jorstad, S. G. et al. Kinematics of parsec-scale jets of gamma-ray blazars at 43 GHz within the VLBA-BU-BLAZAR program. Astrophys. J. 846, 98 (2017).
Agudo, I. et al. POLAMI: Polarimetric Monitoring of AGN at Millimetre Wavelengths—I. The programme, calibration and calibrator data products. Mon. Not. R. Astron. Soc. 474, 1427–1435 (2018).
Agudo, I. et al. POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths—III. Characterization of total flux density and polarization variability of relativistic jets. Mon. Not. R. Astron. Soc. 473, 1850–1867 (2018).
Ho, P. T. P., Moran, J. M. & Lo, K. Y. The Submillimeter Array. Astrophys. J. Lett. 616, L1–L6 (2004).
Primiani, R. A. et al. SWARM: \ 32 GHz correlator and VLBI beamformer for the Submillimeter Array. J. Astron. Instrum. 5, 1641006–810 (2016).
Marrone, D. P. & Rao, R. The submillimeter array polarimeter. In Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV, Society of Photo-Optical Instrumentation Engineers Conference Series Vol. 7020 (eds Duncan, W. D. et al.) J.70202B (SPIE, 2008).
Sault, R. J., Teuben, P. J. & Wright, M. C. H. a retrospective view of MIRIAD. In Astronomical Data Analysis Software and Systems IV, Astronomical Society of the Pacific Conference Series Vol. 77 (eds Shaw, R. A. et al.) 433 (1995).
Strohmayer, T. E. X-ray spectro-polarimetry with photoelectric polarimeters. Astrophys. J. 838, 72 (2017).
Marshall, H. L. Analysis of polarimetry data with angular uncertainties. Astron. J. 162, 134 (2021).
Smith, P. S. et al. Coordinated Fermi/optical monitoring of blazars and the great 2009 September gamma-ray flare of 3C 454.3. Preprint at arXiv https://doi.org/10.48550/arXiv.0912.3621 (2009).
Tonry, J. L. et al. ATLAS: a high-cadence all-sky survey system. Publ. Astron. Soc. Pac. 130, 064505 (2018).
Heinze, A. N. et al. A first catalog of variable stars measured by the Asteroid Terrestrial-impact Last Alert System (ATLAS). Astron. J. 156, 241 (2018).
Shingles, L. et al. Release of the ATLAS Forced Photometry server for public use. Transient Name Server AstroNote 7, 1–7 (2021).
Acknowledgements
The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC), 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 IAA-CSIC group acknowledges financial support from the grant CEX2021-001131-S funded by MCIN/AEI/10.13039/501100011033 to the Instituto de Astrofísica de Andalucía-CSIC and through grant PID2019-107847RB-C44. The POLAMI observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The Submillimetre Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Mauna Kea, the location of the SMA, is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. Some of the data reported here are based on observations made with the Nordic Optical Telescope, owned in collaboration with the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOT. We are grateful to V. Braga, M. Monelli and M. Sänchez Benavente for performing the observations at the Nordic Optical Telescope. Part of the French contributions is supported by the Scientific Research National Center (CNRS) and the French spatial agency (CNES). The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grants 80NSSC21K1917 and 80NSSC22K1571, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF and the W.M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. This work was supported by JST, the establishment of university fellowships towards the creation of science and technology innovation, grant number JPMJFS2129. This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant number JP21H01137. This work was also partially supported by the Optical and Near-Infrared Astronomy Inter-University Cooperation Program from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. We are grateful to the observation and operating members of the Kanata Telescope. Some of the data are based on observations collected at the Observatorio de Sierra Nevada, owned and operated by the Instituto de Astrofísica de Andalucía (IAA-CSIC). Further data are based on observations collected at the Centro Astronómico Hispano en Andalucía (CAHA), operated jointly by Junta de Andalucía and Consejo Superior de Investigaciones Científicas (IAA-CSIC). This research has made use of data from the RoboPol programme, a collaboration between Caltech, the University of Crete, IA-FORTH, IUCAA, the MPIfR and the Nicolaus Copernicus University, which was conducted at Skinakas Observatory in Crete, Greece. D.B., S.K., R.S. and N.M., acknowledge support from the European Research Council (ERC) under the European Unions Horizon 2020 Research and Innovation programme under grant agreement no. 771282. C.C. acknowledges support from the European Research Council (ERC) under the HORIZON ERC Grants 2021 programme under grant agreement no. 101040021. The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917 and 80NSSC22K1571, and NASA Swift Guest Investigator grant 80NSSC22K0537. This work was supported by NSF grant AST-2109127. We acknowledge the use of public data from the Swift data archive. Data from the Steward Observatory spectropolarimetric monitoring project were used. This programme is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G and NNX15AU81G. We acknowledge funding to support our NOT observations from the Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland (Academy of Finland grant no 306531). This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284 and 80NSSC18K1575; by-products of the NEO search include images and catalogues from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen’s University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory and The Millennium Institute of Astrophysics (MAS), Chile. The Very Long Baseline Array is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.
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L.D.G. performed the analysis and led the writing of the paper. H.L.M., S.R.E., D.E.K., F. Muleri and A.D.M. contributed to the IXPE data analysis. I.D., F. Tavecchio, R.W.R., A.P.M. and S.G.J. contributed to the discussion and other parts of the paper, and the latter two provided the VLBA images. I.L. coordinated the multiwavelength observations. I.L. and S.K. contributed the random walk simulations. I.A., C.C., J.E., M.A.G., I. Myserlis, R.R and G.K.K. contributed the radio observations. S.G.J. contributed the infrared observations. S.S.S. performed modelling of the host galaxy in the H band. B.A.-G., F.J.A., I.A., H.A., M.I.B., D.B., G.B., I.G.B., V.C., Y.F., M.G.-C., C.H., R.I., K.S.K., S.K., E.K., P.M.K., E.L., N.M., A. Marchini, T. Mizuno, T.N., S.R., M.S., R.S., A.S., M.U. and A.V. contributed the optical observations. A.A.V. contributed to the paper discussion. R.M., M.P. and S.P. contributed to the Swift data analysis. L.P. and M.N. contributed the Fermi data. The remaining authors are part of the IXPE team whose significant contribution made the X-ray polarization observations possible.
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Di Gesu, L., Marshall, H.L., Ehlert, S.R. et al. Discovery of X-ray polarization angle rotation in the jet from blazar Mrk 421. Nat Astron 7, 1245–1258 (2023). https://doi.org/10.1038/s41550-023-02032-7
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DOI: https://doi.org/10.1038/s41550-023-02032-7
