Ursini, FrancescoFrancescoUrsiniGnarini, A.A.GnariniBIANCHI, SimoneSimoneBIANCHIBobrikova, A.A.BobrikovaCAPITANIO, FIAMMAFIAMMACAPITANIOCOCCHI, MassimoMassimoCOCCHIFABIANI, SergioSergioFABIANIFARINELLI, RubenRubenFARINELLIKaaret, P.P.KaaretMatt, G.G.MattNg, M.M.NgPoutanen, J.J.PoutanenRavi, S.S.RaviTarana, A.A.Tarana2025-05-162025-05-1620240004-6361http://hdl.handle.net/20.500.12386/37147We 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.STAMPAenArticle10.1051/0004-6361/2024515842-s2.0-85206973557https://www.aanda.org/articles/aa/full_html/2024/10/aa51584-24/aa51584-24.htmlhttps://api.elsevier.com/content/abstract/scopus_id/852069735572024A&A...690A.200UFIS/05 - ASTRONOMIA E ASTROFISICA