A1 Refereed original research article in a scientific journal
First spectropolarimetric observation of the neutron star low-mass X-ray binary GX 3+1
Authors: Gnarini, Andrea; Farinelli, Ruben; Ursini, Francesco; Bianchi, Stefano; Capitanio, Fiamma; Matt, Giorgio; Ng, Mason; Tarana, Antonella; Bobrikova, Anna; Cocchi, Massimo; Fabiani, Sergio; Kaaret, Philip; Poutanen, Juri; Ravi, Swati
Publisher: EDP SCIENCES S A
Publishing place: LES ULIS CEDEX A
Publication year: 2024
Journal: Astronomy and Astrophysics
Journal name in source: ASTRONOMY & ASTROPHYSICS
Journal acronym: ASTRON ASTROPHYS
Article number: A123
Volume: 692
Number of pages: 7
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202452642(external)
Web address : https://doi.org/10.1051/0004-6361/202452642(external)
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/478066523(external)
We report the first simultaneous X-ray spectropolarimetric observation of the bright atoll neutron star low-mass X-ray binary GX 3+1, performed by the Imaging X-ray Polarimetry Explorer (IXPE) joint with NICER and NuSTAR. The source does not exhibit significant polarization in the 2–8 keV energy band, with an upper limit of 1.3% at a 99% confidence level on the polarization degree. The observed spectra can be well described by a combination of thermal disk emission, the hard Comptonization component, and reflected photons off the accretion disk. In particular, from the broad Fe Kα line profile, we were able to determine the inclination of the system (i ≈ 36◦ ), which is crucial for comparing the observed polarization with theoretical models. Both the spectral and polarization properties of GX 3+1 are consistent with those of other atoll sources observed by IXPE. Therefore, we may expect a similar geometrical configuration for the accreting system and the hot Comptonizing region. The low polarization is also consistent with the low inclination of the system.
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