CaltechAUTHORS
Published December 10, 2022 | Version Published
Journal Article Open

The X-Ray Polarimetry View of the Accreting Pulsar Cen X-3

Creators

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

Abstract

The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in the presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ∼20 in flux. In the low-luminosity state, no significant polarization was found in either pulse phase-averaged (with a 3σ upper limit of 12%) or phase-resolved (the 3σ upper limits are 20%–30%) data. In the bright state, the polarization degree of 5.8% ± 0.3% and polarization angle of 49.°6 ± 1.°5 with a significance of about 20σ were measured from the spectropolarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anticorrelation between the flux and the polarization degree, as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49° and a magnetic obliquity of 17°. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 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) with agreements 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). We acknowledge support from Russian Science Foundation grant 20-12-00364 (S.S.T., J.P., V.F.S.); Academy of Finland grants 333112, 349144, 349373, and 349906 (S.S.T., J.P.); German Academic Exchange Service (DAAD) travel grant 57525212 (V.D., V.F.S.); German Research Foundation (DFG) grant WE 1312/53-1 (V.F.S.); the UKRI Stephen Hawking fellowship; and the Netherlands Organization for Scientific Research Veni fellowship (A.A.M.). Facility: IXPE. - Software: astropy (Astropy Collaboration et al. 2013, 2018), xspec (Arnaud 1996), ixpeobssim (Baldini et al. 2022), emcee (Foreman-Mackey et al. 2013).

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Additional details

Identifiers

Eprint ID
119615
Resolver ID
CaltechAUTHORS:20230301-701033500.20

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)
Russian Science Foundation
20-12-00364
Academy of Finland
333112
Academy of Finland
349144
Academy of Finland
349373
Academy of Finland
349906
Deutscher Akademischer Austauschdienst (DAAD)
57525212
Deutsche Forschungsgemeinschaft (DFG)
WE 1312/53-1
UK Research and Innovation
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)

Dates

Created
2023-05-08
Created from EPrint's datestamp field
Updated
2023-05-08
Created from EPrint's last_modified field

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