The first X-ray polarimetry of an eclipsing low-mass X-ray binary : serendipitous IXPE observation of AX J1745.6–2901;
: Mikušincová, Romana; Marra, Lorenzo; Manikantan, Hemanth; Bianchi, Stefano; Capitanio, Fiamma; Chakraborty, Sudip; Ciancarella, Raul; Costa, Enrico; De Angelis, Nicolas; Del Santo, Melania; Fabiani, Sergio; Ferrazzoli, Riccardo; Gianolli, Vittoria E.; Gnarini, Andrea; Ingram, Adam; Mandel, Shifra; Mastroserio, Guglielmo; Matt, Giorgio; Mori, Kaya; Muleri, Fabio; Pagliarella, Simone; Parra, Maxime; Petrucci, P.O.; Podgorný, Jakub; Poutanen, Juri; Ravi, Swati; Soffitta, Paolo; Steiner, James F.; Tarana, Antonella; Taverna, Roberto; Ursini, Francesco; Veledina, Alexandra; Vincentelli, Federico M.; Yilmaz, Anastasiya; De Marco, Barbara; Gupta, Maitrayee; Loktev, Vladislav; Russell, Thomas D.; Svoboda, Jiří; Tombesi, Francesco; Zhang, Shuo
Publisher: Institute of Physics Publishing
: 2026
Astrophysical Journal
: 122
: 1005
: 1
: 0004-637X
: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ae7341
: https://doi.org/10.3847/1538-4357/ae7341
: https://research.utu.fi/converis/portal/detail/Publication/527167421
We present the first X-ray polarimetric measurement of the neutron star low-mass X-ray binary system AX J1745.6−2901 conducted by the Imaging X-ray Polarimetry Explorer (IXPE) satellite. This transient source, located within ∼1'.5 of the Galactic center, was observed serendipitously during a MAXI J1744−294 observation with a duration of 150 ks. The complex nature of the region in which AX J1745.6−2901 is located poses a challenge for studying its polarization. By performing a detailed analysis of the contamination from MAXI J1744−294 and the Galactic center diffuse emission, we find the source polarization degree PD = 14.7% ± 4.0% and polarization angle PA = 122° ± 8°. The phase-resolved analysis shows increase in polarization during the eclipse phase, with PD = 34.2% ± 8.7%, suggesting that the polarization-inducing mechanisms are of scattering nature, probably originating from disk winds.
accretion, neutron stars, polarimetry, X-ray astronomy, X-ray binary stars
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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-2022-13-I.0, agreements ASI-INAF-2022-19-HH.1-2026 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF 2025-33-HH.0 and ASI-INFN 2026-5-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).
A.G. was supported by an appointment to the NASA Postdoctoral Program at the Marshall Space Flight Center (MSFC), administered by Oak Ridge Associated Universities under contract with NASA. A.I. acknowledges support by the European Union (ERC, X-MAPS, 101169908). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. A.V. acknowledges support from the Research Council of Finland grants 355672 and 372881 and the Centre of Excellence in Neutron-Star Physics (grant 374064). Nordita is supported in part by NordForsk. The French contribution is supported by the French Space Agency (Centre National d’Etudes Spatiales, CNES) and the Action Thématique Processus Extrême et Multimessager of the French CNRS. J.P. and J.S. acknowledge GACR support from the project 26-22614S and the institutional support from RVO:67985815. F.C., A.T., and S.F. acknowledge financial support by the Istituto Nazionale di Astrofisica (INAF) grant 1.05.24.02.04. V.E.G. acknowledges funding under NASA contract 80NSSC24K1403. The USRA coauthors gratefully acknowledge NASA funding through contract 80NSSC24M0035. F.M.V. acknowledges support from the the European Union’s Horizon Europe research and innovation program with the Marie Skłodowska-Curie (grant agreement No. 101149685). B.D.M. acknowledges support via a Ramón y Cajal Fellowship (RYC2018-025950-I), the Spanish MINECO grants PID2023-148661NB-I00, PID2022-136828NB-C44, and the AGAUR/Generalitat de Catalunya grant SGR-386/2021.
