Marshall, Herman L.Herman L.MarshallNg, MasonMasonNgRogantini, DanieleDanieleRogantiniHeyl, JeremyJeremyHeylTsygankov, Sergey S.Sergey S.TsygankovPoutanen, JuriJuriPoutanenCOSTA, ENRICOENRICOCOSTAZane, SilviaSilviaZaneMALACARIA, ChristianChristianMALACARIAAgudo, IvánIvánAgudoANTONELLI, Lucio AngeloLucio AngeloANTONELLIBACHETTI, MatteoMatteoBACHETTIBaldini, LucaLucaBaldiniBaumgartner, Wayne H.Wayne H.BaumgartnerBellazzini, RonaldoRonaldoBellazziniBianchi, StefanoStefanoBianchiBongiorno, Stephen D.Stephen D.BongiornoBonino, RaffaellaRaffaellaBoninoBrez, AlessandroAlessandroBrezBUCCIANTINI, Niccolo'Niccolo'BUCCIANTINICAPITANIO, FIAMMAFIAMMACAPITANIOCastellano, SimoneSimoneCastellanoCavazzuti, ElisabettaElisabettaCavazzutiCiprini, StefanoStefanoCipriniDE ROSA, AlessandraAlessandraDE ROSADEL MONTE, EttoreEttoreDEL MONTEDi Gesu, LauraLauraDi GesuDi Lalla, NiccolòNiccolòDi LallaDI MARCO, AlessandroAlessandroDI MARCODonnarumma, ImmacolataImmacolataDonnarummaDoroshenko, VictorVictorDoroshenkoDovčiak, MichalMichalDovčiakEhlert, Steven R.Steven R.EhlertEnoto, TeruakiTeruakiEnotoEVANGELISTA, YURIYURIEVANGELISTAFABIANI, SergioSergioFABIANIFERRAZZOLI, RiccardoRiccardoFERRAZZOLIGarcia, Javier A.Javier A.GarciaGunji, ShuichiShuichiGunjiHayashida, KiyoshiKiyoshiHayashidaIwakiri, WataruWataruIwakiriJorstad, Svetlana G.Svetlana G.JorstadKaras, VladimirVladimirKarasKitaguchi, TakaoTakaoKitaguchiKolodziejczak, Jeffery J.Jeffery J.KolodziejczakKrawczynski, HenricHenricKrawczynskiLA MONACA, FabioFabioLA MONACALatronico, LucaLucaLatronicoLiodakis, IoannisIoannisLiodakisMaldera, SimoneSimoneMalderaManfreda, AlbertoAlbertoManfredaMarin, FrédéricFrédéricMarinMarinucci, AndreaAndreaMarinucciMarscher, Alan P.Alan P.MarscherMatt, GiorgioGiorgioMattMitsuishi, IkuyukiIkuyukiMitsuishiMizuno, TsunefumiTsunefumiMizunoMULERI, FABIOFABIOMULERINg, C. -Y.C. -Y.NgO'Dell, Stephen L.Stephen L.O'DellOmodei, NicolaNicolaOmodeiOppedisano, ChiaraChiaraOppedisanoPAPITTO, ALESSANDROALESSANDROPAPITTOPavlov, George G.George G.PavlovPeirson, Abel L.Abel L.PeirsonPERRI, MatteoMatteoPERRIPesce-Rollins, MelissaMelissaPesce-RollinsPetrucci, Pierre-OlivierPierre-OlivierPetrucciPILIA, MauraMauraPILIAPOSSENTI, ANDREAANDREAPOSSENTIPuccetti, SimonettaSimonettaPuccettiRamsey, Brian D.Brian D.RamseyRANKIN, JohnJohnRANKINRATHEESH, AJAYAJAYRATHEESHRomani, Roger W.Roger W.RomaniSgrò, CarmeloCarmeloSgròSlane, PatrickPatrickSlaneSOFFITTA, PAOLOPAOLOSOFFITTASpandre, GloriaGloriaSpandreTamagawa, ToruToruTamagawaTAVECCHIO, FabrizioFabrizioTAVECCHIOTaverna, RobertoRobertoTavernaTawara, YuzuruYuzuruTawaraTennant, Allyn F.Allyn F.TennantThomas, Nicholas E.Nicholas E.ThomasTOMBESI, FrancescoFrancescoTOMBESITROIS, ALESSIOALESSIOTROISTurolla, RobertoRobertoTurollaVink, JaccoJaccoVinkWeisskopf, Martin C.Martin C.WeisskopfWu, KinwahKinwahWuXIE, FEIFEIXIEIXPE CollaborationSchulz, Norbert S.Norbert S.SchulzChakrabarty, DeeptoDeeptoChakrabarty2025-02-282025-02-2820220004-637Xhttp://hdl.handle.net/20.500.12386/36309We present measurements of the polarization of X-rays in the 2-8 keV band from the pulsar in the ultracompact low-mass X-ray binary 4U 1626-67 using data from the Imaging X-Ray Polarimetry Explorer (IXPE). The 7.66 s pulsations were clearly detected throughout the IXPE observations as well as in the NICER soft X-ray observations, which we used as the basis for our timing analysis and to constrain the spectral shape over the 0.4-10 keV energy band. Chandra HETGS high-resolution X-ray spectra were also obtained near the times of the IXPE observations for firm spectral modeling. We found an upper limit on the pulse-averaged linear polarization of <4% (at 95% confidence). Similarly, there was no significant detection of polarized flux in pulse phase intervals when subdividing the bandpass by energy. However, spectropolarimetric modeling over the full bandpass in pulse phase intervals provided a marginal detection of polarization of the power-law spectral component at the 4.8% ± 2.3% level (90% confidence). We discuss the implications concerning the accretion geometry onto the pulsar, favoring two-component models of the pulsed emission....STAMPAenArticle10.3847/1538-4357/ac98c22-s2.0-85143143326https://api.elsevier.com/content/abstract/scopus_id/85143143326https://iopscience.iop.org/article/10.3847/1538-4357/ac98c2FIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation