CaltechAUTHORS
Published July 1, 2023 | Version Supplemental Material
Journal Article Open

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

Creators

  • 1. ROR icon Observatory of Strasbourg
  • 2. ROR icon Max Planck Institute for Astrophysics
  • 3. ROR icon Space Research Institute
  • 4. ROR icon Ludwig-Maximilians-Universität München
  • 5. ROR icon Institute for Space Astrophysics and Planetology
  • 6. ROR icon Agenzia Spaziale Italiana
  • 7. ROR icon Astronomical Observatory of Rome
  • 8. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 9. ROR icon Roma Tre University
  • 10. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 11. ROR icon RIKEN
  • 12. ROR icon Instituto de Astrofísica de Andalucía
  • 13. ROR icon Osservatorio Astronomico di Cagliari
  • 14. ROR icon INFN Sezione di Pisa
  • 15. ROR icon University of Pisa
  • 16. ROR icon Marshall Space Flight Center
  • 17. ROR icon INFN Sezione di Torino
  • 18. ROR icon University of Turin
  • 19. ROR icon Arcetri Astrophysical Observatory
  • 20. ROR icon University of Florence
  • 21. ROR icon INFN Sezione di Firenze
  • 22. ROR icon Universities Space Research Association
  • 23. ROR icon INFN Sezione di Roma II
  • 24. ROR icon Stanford University
  • 25. ROR icon University of Tübingen
  • 26. ROR icon Astronomical Institute
  • 27. ROR icon California Institute of Technology
  • 28. ROR icon Yamagata University
  • 29. ROR icon Osaka University
  • 30. ROR icon University of British Columbia
  • 31. ROR icon Newcastle University
  • 32. ROR icon Chuo University
  • 33. ROR icon Chiba University
  • 34. ROR icon Boston University
  • 35. ROR icon St Petersburg University
  • 36. ROR icon University of Iowa
  • 37. ROR icon Washington University in St. Louis
  • 38. ROR icon University of Turku
  • 39. ROR icon Massachusetts Institute of Technology
  • 40. ROR icon Nagoya University
  • 41. ROR icon Hiroshima University
  • 42. ROR icon University of Maryland, Baltimore County
  • 43. ROR icon Goddard Space Flight Center
  • 44. ROR icon University of Hong Kong
  • 45. ROR icon Pennsylvania State University
  • 46. ROR icon Brera Astronomical Observatory
  • 47. ROR icon University of Padua
  • 48. ROR icon University of Rome Tor Vergata
  • 49. ROR icon University of Maryland, College Park
  • 50. ROR icon University College London
  • 51. ROR icon University of Amsterdam
  • 52. ROR icon Guangxi University

Abstract

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.

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Additional details

Identifiers

Eprint ID
122089
Resolver ID
CaltechAUTHORS:20230630-22232000.4

Funding

NASA
NNM15AA18C
Agenzia Spaziale Italiana (ASI)
ASI-OHBI-2017-12-I.0
Agenzia Spaziale Italiana (ASI)
ASI-INAF-2017-12-H0
Agenzia Spaziale Italiana (ASI)
ASI-INFN-2017.13-H0
Agenzia Spaziale Italiana (ASI)
ASI-INAF-2022-14-HH.0
Agenzia Spaziale Italiana (ASI)
ASI-INFN 2021-43-HH.0
Istituto Nazionale di Astrofisica (INAF)
Istituto Nazionale di Fisica Nucleare (INFN)
European Research Council (ERC)
882679
Programme National Hautes Energies (PNHE)
Centre National de la Recherche Scientifique (CNRS)
Centre National d'Études Spatiales (CNES)
Ministerio de Ciencia e Innovación (MCIN)
MCIN/AEI/10.13039/501100011033/
Severo Ochoa Centre of Excellence
CEX2021-001131-S
Ministerio de Ciencia e Innovación (MCIN)
PID2019-107847RB-C44
Ministerio de Ciencia e Innovación (MCIN)
PID2022-139117NB-C44
Royal Society
NASA
GO1-22136X
Smithsonian Institution
NASA
NAS8-03060
University of Hong Kong
HKU 17305419

Dates

Created
2023-07-01
Created from EPrint's datestamp field
Updated
2023-07-01
Created from EPrint's last_modified field

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