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Published July 1, 2023 | Supplemental Material
Journal Article Open

X-ray polarization evidence for a 200-year-old flare of Sgr A*

Marin, Frédéric ORCID icon
Churazov, Eugene ORCID icon
Khabibullin, Ildar ORCID icon
Ferrazzoli, Riccardo ORCID icon
Di Gesu, Laura ORCID icon
Barnouin, Thibault ORCID icon
Di Marco, Alessandro ORCID icon
Middei, Riccardo ORCID icon
Vikhlinin, Alexey
Costa, Enrico ORCID icon
Soffitta, Paolo ORCID icon
Muleri, Fabio ORCID icon
Sunyaev, Rashid ORCID icon
Forman, William R. ORCID icon
Kraft, Ralph ORCID icon
Bianchi, Stefano ORCID icon
Donnarumma, Immacolata ORCID icon
Petrucci, Pierre-Olivier ORCID icon
Enoto, Teruaki ORCID icon
Agudo, Iván ORCID icon
Antonelli, Lucio A. ORCID icon
Bachetti, Matteo ORCID icon
Baldini, Luca ORCID icon
Baumgartner, Wayne H. ORCID icon
Bellazzini, Ronaldo ORCID icon
Bongiorno, Stephen D. ORCID icon
Bonino, Raffaella ORCID icon
Brez, Alessandro ORCID icon
Bucciantini, Niccolò ORCID icon
Capitanio, Fiamma ORCID icon
Castellano, Simone ORCID icon
Cavazzuti, Elisabetta ORCID icon
Chen, Chien-Ting ORCID icon
Ciprini, Stefano ORCID icon
De Rosa, Alessandra ORCID icon
Del Monte, Ettore ORCID icon
Di Lalla, Niccolò ORCID icon
Doroshenko, Victor ORCID icon
Dovčiak, Michal ORCID icon
Ehlert, Steven R. ORCID icon
Evangelista, Yuri ORCID icon
Fabiani, Sergio ORCID icon
García, Javier A. ORCID icon
Gunji, Shuichi ORCID icon
Hayashida, Kiyoshi ORCID icon
Heyl, Jeremy ORCID icon
Ingram, Adam ORCID icon
Iwakiri, Wataru ORCID icon
Jorstad, Svetlana G. ORCID icon
Kaaret, Philip ORCID icon
Karas, Vladimir ORCID icon
Kitaguchi, Takao
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
Marinucci, Andrea ORCID icon
Marscher, Alan P. ORCID icon
Marshall, Herman L. ORCID icon
Massaro, Francesco ORCID icon
Matt, Giorgio ORCID icon
Mitsuishi, Ikuyuki
Mizuno, Tsunefumi ORCID icon
Negro, Michela ORCID icon
Ng, C.-Y. ORCID icon
O'Dell, Stephen L. ORCID icon
Omodei, Nicola ORCID icon
Oppedisano, Chiara ORCID icon
Papitto, Alessandro ORCID icon
Pavlov, George G. ORCID icon
Peirson, Abel L. ORCID icon
Perri, Matteo ORCID icon
Pesce-Rollins, Melissa ORCID icon
Pilia, Maura ORCID icon
Possenti, Andrea ORCID icon
Poutanen, Juri ORCID icon
Puccetti, Simonetta ORCID icon
Ramsey, Brian D. ORCID icon
Rankin, John ORCID icon
Ratheesh, Ajay ORCID icon
Roberts, Oliver J. ORCID icon
Romani, Roger W. ORCID icon
Sgrò, Carmelo ORCID icon
Slane, Patrick 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, Nicholas E. ORCID icon
Tombesi, Francesco ORCID icon
Trois, Alessio ORCID icon
Tsygankov, Sergey S. ORCID icon
Turolla, Roberto ORCID icon
Vink, Jacco ORCID icon
Weisskopf, Martin C. ORCID icon
Wu, Kinwah ORCID icon
Xie, Fei ORCID icon
Zane, Silvia ORCID icon


The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A* (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei1. Reflection of X-rays from Sgr A* by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years2. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A* are consistent with the reflection scenario3,4,5. If this interpretation is correct, the reflected continuum emission should be polarized6. Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of −48° ± 11°. The polarization angle is consistent with Sgr A* being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A* was briefly comparable to that of a Seyfert galaxy.

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, with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by 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 with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica and the Istituto Nazionale di Fisica Nucleare in Italy. This research used data products provided by the IXPE team (the Marshall Space Flight Center, the Space Science Data Center, the Istituto Nazionale di Astrofisica and the Istituto Nazionale di Fisica Nucleare) and distributed with additional software tools by the HEASARC, at the NASA Goddard Space Flight Center. F.M. is grateful to the Astronomical Observatory of Strasbourg, the Centre National de la Recherche Scientifique and the University of Strasbourg under whose benevolence this paper was written. I.K. acknowledges support by the COMPLEX project from the European Research Council under the European Union's Horizon 2020 research and innovation programme grant agreement ERC-2019-AdG 882679. P.-O.P. acknowledges financial support from the French National Program of High Energy (PNHE)/Centre National de la Recherche Scientifique and from the French national space agency (Centre National d'Etudes Spatiales (CNES)). I.A. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación (MCIN/AEI/ 10.13039/501100011033) through the Center of Excellence Severo Ochoa award for the Instituto de Astrofísica de Andalucía-CSIC (CEX2021-001131-S), and through grants PID2019-107847RB-C44 and PID2022-139117NB-C44. A.I. acknowledges support from the Royal Society. A.V., W.F. and R.K. acknowledge support from NASA grant GO1-22136X, the Smithsonian Institution, and the Chandra High Resolution Camera Project through NASA contract NAS8-03060. C.-Y.N. is supported by a GRF grant of the Hong Kong Government under HKU 17305419. Contributions. F. M. led the IXPE observation, contributed to the analysis and led the writing of the paper. E. C., I.K., R.F., L.D.G., T.B., A.D.M., R.M., E. C., P. S., F. M., R.S. and P.K. contributed to the IXPE analysis, discussion and writing of the paper. A.V., W.F. and R.K. provided and reduced the Chandra data used in this paper. S.B., I.D., P.-O.P. and T.E. contributed with discussion and parts of the paper. The remaining authors are part of the IXPE team whose substantial contribution made the satellite and the Galactic Centre observation possible. Data availability. The IXPE data that support the findings of this study are freely available in the HEASARC IXPE data archive (https://heasarc.gsfc.nasa.gov/docs/ixpe/archive/). The XMM-Newton data can be found on the same website, and the Chandra data will be public after one year from the observation date. Code availability. The analysis and simulation software ixpeobssim developed by the IXPE collaboration and its documentation are available publicly through https://ixpeobssim.readthedocs.io/en/latest/?badge=latest.494. XSPEC is distributed and maintained under the aegis of the HEASARC and can be downloaded as part of HEAsoft from http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/download.html. The authors declare no competing interests.

Attached Files

Supplemental Material - 41586_2023_6064_Fig5_ESM.jpg

Supplemental Material - 41586_2023_6064_Fig6_ESM.jpg

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Supplemental Material - 41586_2023_6064_Tab2_ESM.jpg


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Additional details

August 22, 2023
October 20, 2023