A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
X-ray spectropolarimetry of the bright atoll Serpens X-1
Tekijät: Ursini, F.; Gnarini, A.; Bianchi, S.; Bobrikova, A.; Capitanio, F.; Cocchi, M.; Fabiani, S.; Farinelli, R.; Kaaret, P.; Matt, G.; Ng, M.; Poutanen, J.; Ravi, S.; Tarana, A.
Kustantaja: EDP Sciences
Julkaisuvuosi: 2024
Journal: Astronomy and Astrophysics
Tietokannassa oleva lehden nimi: Astronomy and Astrophysics
Artikkelin numero: A200
Vuosikerta: 690
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202451584
Verkko-osoite: https://doi.org/10.1051/0004-6361/202451584
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/458966958
We present simultaneous X-ray polarimetric and spectral observations of the bright atoll source Ser X-1 carried out with the Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR. We obtain an upper limit of 2% (99% confidence level) on the polarization degree in the 2 8 keV energy band. We detect four type-I X-ray bursts, two of which during the IXPE observation. This is the first time that has IXPE observed type-I X-ray bursts, and it allows us to place an upper limit on their polarization degree; however, due to the limited total number of counts in each burst, we obtain a relatively high upper limit (80%). We confirm the presence of reflection features in the X-ray spectrum, notably a broad iron line. Fitting the data with a relativistic reflection model, we derive a disk inclination of 25. The spectral and polarization properties are comparable with other atolls observed by IXPE, suggesting a similar accretion geometry, and the relatively low polarization is consistent with the low inclination.
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Julkaisussa olevat rahoitustiedot:
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). The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. FU, AG, SB, FC, and GM acknowledge financial support by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-INAF-2022-19-HH.0. SF has been supported by the project PRIN 2022 – 2022LWPEXW – “An X-ray view of compact objects in polarized light”, CUP C53D23001180006. AB acknowledges support from the Finnish Cultural Foundation grant 00240328. JP thanks the Academy of Finland grant 333112 for support. F.C. acknowledges support by the Istituto Nazionale di Astrofisica (INAF) grant 1.05.23.05.06: “Spin and Geometry in accreting X-ray binaries: The first multi frequency spectro-polarimetric campaign”.
