Veledina, A.A.VeledinaMuleri, F.F.MuleriDovčiak, M.M.DovčiakPoutanen, J.J.PoutanenRatheesh, A.A.RatheeshCapitanio, F.F.CapitanioMatt, G.G.MattSoffitta, P.P.SoffittaTennant, A.F.A.F.TennantNegro, M.M.NegroKaaret, P.P.KaaretCosta, E.E.CostaIngram, A.A.IngramSvoboda, J.J.SvobodaKrawczynski, H.H.KrawczynskiBianchi, S.S.BianchiSteiner, J.F.J.F.SteinerGarcía, J.A.J.A.GarcíaKravtsov, V.V.KravtsovNitindala, A.P.A.P.NitindalaEwing, M.M.EwingMastroserio, G.G.MastroserioMarinucci, AndreaAndreaMarinucciUrsini, F.F.UrsiniTombesi, F.F.TombesiTsygankov, S.S.S.S.TsygankovYang, Y.-J.Y.-J.YangWeisskopf, M.C.M.C.WeisskopfTrushkin, S.A.S.A.TrushkinEgron, E.E.EgronIacolina, Maria NoemiMaria NoemiIacolinaPilia, M.M.PiliaMarra, L.L.MarraMikušincová, R.R.MikušincováNathan, E.E.NathanParra, M.M.ParraPetrucci, P.-O.P.-O.PetrucciPodgorný, J.J.PodgornýTugliani, S.S.TuglianiZane, S.S.ZaneZhang, W.W.ZhangAgudo, I.I.AgudoAntonelli, L.A.L.A.AntonelliBachetti, M.M.BachettiBaldini, L.L.BaldiniBaumgartner, W.H.W.H.BaumgartnerBellazzini, R.R.BellazziniBongiorno, S.D.S.D.BongiornoBonino, R.R.BoninoBrez, A.A.BrezBucciantini, N.N.BucciantiniCastellano, S.S.CastellanoCavazzuti, ElisabettaElisabettaCavazzutiChen, C.-T.C.-T.ChenCiprini, StefanoStefanoCipriniDe Rosa, A.A.De RosaDel Monte, E.E.Del MonteDi Gesù, LauraLauraDi GesùDi Lalla, N.N.Di LallaDi Marco, A.A.Di MarcoDonnarumma, ImmacolataImmacolataDonnarummaDoroshenko, V.V.DoroshenkoEhlert, S.R.S.R.EhlertEnoto, T.T.EnotoEvangelista, Y.Y.EvangelistaFabiani, S.S.FabianiFerrazzoli, R.R.FerrazzoliGunji, S.S.GunjiHayashida, K.K.HayashidaHeyl, J.J.HeylIwakiri, W.W.IwakiriJorstad, S.G.S.G.JorstadKaras, V.V.KarasKislat, F.F.KislatKitaguchi, T.T.KitaguchiKolodziejczak, J.J.J.J.KolodziejczakLa Monaca, F.F.La MonacaLatronico, L.L.LatronicoLiodakis, I.I.LiodakisMaldera, S.S.MalderaManfreda, A.A.ManfredaMarin, F.F.MarinMarscher, A.P.A.P.MarscherMarshall, H.L.H.L.MarshallMassaro, F.F.MassaroMitsuishi, I.I.MitsuishiMizuno, T.T.MizunoNg, C.-Y.C.-Y.NgO’Dell, S.L.S.L.O’DellOmodei, N.N.OmodeiOppedisano, C.C.OppedisanoPapitto, A.A.PapittoPavlov, G.G.G.G.PavlovPeirson, A.L.A.L.PeirsonPerri, M.M.PerriPesce-Rollins, M.M.Pesce-RollinsPossenti, A.A.PossentiPuccetti, S.S.PuccettiRamsey, B.D.B.D.RamseyRankin, J.J.RankinRoberts, O.J.O.J.RobertsRomani, R.W.R.W.RomaniSgrò, C.C.SgròSlane, P.P.SlaneSpandre, G.G.SpandreSwartz, D.A.D.A.SwartzTamagawa, T.T.TamagawaTavecchio, F.F.TavecchioTaverna, R.R.TavernaTawara, Y.Y.TawaraThomas, N.E.N.E.ThomasTrois, A.A.TroisTurolla, R.R.TurollaVink, J.J.VinkWu, K.K.WuXie, F.F.Xie2024-05-162024-05-162023-11-21https://hdl.handle.net/20.500.13025/6442We report the first detection of the X-ray polarization of the bright transient Swift J1727.8−1613 with the Imaging X-ray Polarimetry Explorer. The observation was performed at the beginning of the 2023 discovery outburst, when the source resided in the bright hard state. We find a time- and energy-averaged polarization degree of 4.1% ± 0.2% and a polarization angle of 2.°2 ± 1.°3 (errors at 68% confidence level; this translates to ∼20σ significance of the polarization detection). This finding suggests that the hot corona emitting the bulk of the detected X-rays is elongated, rather than spherical. The X-ray polarization angle is consistent with that found in submillimeter wavelengths. Since the submillimeter polarization was found to be aligned with the jet direction in other X-ray binaries, this indicates that the corona is elongated orthogonal to the jet. © 2023. The Author(s). Published by the American Astronomical Society.enjournal article10.3847/2041-8213/ad0781