Complex rotational dynamics of the neutron star in Hercules X-1 revealed by X-ray polarization

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, with industry partner Ball Aerospace (Contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Contract ASI-ASI-OHBI-2022-13-I.0 and Agreements ASI-INAF-2022-19-HH.0 and ASI-INFN-2017.13-H0) and its Space Science Data Center (Agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0), and by the Italian National Institute for Astrophysics and the Italian National Institute for Nuclear Physics. This research used data products provided by the IXPE Team (Marshall Space Flight Center, Space Science Data Center, Italian National Institute for Astrophysics and Italian National Institute for Nuclear Physics) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center at NASA’s Goddard Space Flight Center. 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 program, and computational resources and services provided by Compute Canada, Advanced Research Computing at the University of British Columbia, and the SciServer science platform (www.sciserver.org). D.G.-C. acknowledges support from a fellowship grant from the French National Centre for Space Studies. J.P. and S.S.T. were supported by the Academy of Finland (Grant Nos. 333112 and 349144) and the Väisälä Foundation. V.D. and V.F.S. thank the German Academic Exchange Service (Travel Grant No. 57525212). We used Astropy (http://www.astropy.org), a community-developed core Python package and an ecosystem of tools and resources for astronomy.

The data used for this analysis are available through High-Energy Astrophysics Science Archive Research Center under IXPE Observation IDs 01001899, 02003801 and 02004001.

The software used for this analysis is available at https://github.com/UBC-Astrophysics/IXPE-Analysis.

The authors declare that they have no competing financial interests.