@article{discovery10196156,
          volume = {8},
           month = {August},
       publisher = {Springer Science and Business Media LLC},
            note = {This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.},
           pages = {1031--1046},
         journal = {Nature Astronomy},
            year = {2024},
           title = {Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE},
            issn = {2397-3366},
        keywords = {Compact astrophysical objects, High-energy astrophysics},
          author = {Veledina, Alexandra and Muleri, Fabio and Poutanen, Juri and Podgorn{\'y}, Jakub and Dov{\vc}iak, Michal and Capitanio, Fiamma and Churazov, Eugene and De Rosa, Alessandra and Di Marco, Alessandro and Forsblom, Sofia V and Kaaret, Philip and Krawczynski, Henric and La Monaca, Fabio and Loktev, Vladislav and Lutovinov, Alexander A and Molkov, Sergey V and Mushtukov, Alexander A and Ratheesh, Ajay and Rodriguez Cavero, Nicole and Steiner, James F and Sunyaev, Rashid A and Tsygankov, Sergey S and Weisskopf, Martin C and Zdziarski, Andrzej A and Bianchi, Stefano and Bright, Joe S and Bursov, Nikolaj and Costa, Enrico and Egron, Elise and Garcia, Javier A and Green, David A and Gurwell, Mark and Ingram, Adam and Kajava, Jari JE and Kale, Ruta and Kraus, Alex and Malyshev, Denys and Marin, Fr{\'e}d{\'e}ric and Matt, Giorgio and McCollough, Michael and Mereminskiy, Ilya A and Nizhelsky, Nikolaj and Piano, Giovanni and Pilia, Maura and Pittori, Carlotta and Rao, Ramprasad and Righini, Simona and Soffitta, Paolo and Shevchenko, Anton and Svoboda, Jiri and Tombesi, Francesco and Trushkin, Sergei A and Tsybulev, Peter and Ursini, Francesco and Wu, Kinwah and Agudo, Iv{\'a}n and Antonelli, Lucio A and Bachetti, Matteo and Baldini, Luca and Baumgartner, Wayne H and Bellazzini, Ronaldo and Bongiorno, Stephen D and Bonino, Raffaella and Brez, Alessandro and Bucciantini, Niccol{\`o} and Castellano, Simone and Cavazzuti, Elisabetta and Chen, Chien-Ting and Ciprini, Stefano and Del Monte, Ettore and Di Gesu, Laura and Di Lalla, Niccol{\`o} and Donnarumma, Immacolata and Doroshenko, Victor and Ehlert, Steven R and Enoto, Teruaki and Evangelista, Yuri and Fabiani, Sergio and Ferrazzoli, Riccardo and Gunji, Shuichi and Hayashida, Kiyoshi and Heyl, Jeremy and Iwakiri, Wataru and Jorstad, Svetlana G and Karas, Vladimir and Kislat, Fabian and Kitaguchi, Takao and Kolodziejczak, Jeffery J and Latronico, Luca and Liodakis, Ioannis and Maldera, Simone and Manfreda, Alberto and Marinucci, Andrea and Marscher, Alan P and Marshall, Herman L and Massaro, Francesco and Mitsuishi, Ikuyuki and Mizuno, Tsunefumi and Negro, Michela and Ng, Chi-Yung and O'Dell, Stephen L and Omodei, Nicola and Oppedisano, Chiara and Papitto, Alessandro and Pavlov, George G and Peirson, Abel L and Perri, Matteo and Pesce-Rollins, Melissa and Petrucci, Pierre-Olivier and Possenti, Andrea and Puccetti, Simonetta and Ramsey, Brian D and Rankin, John and Roberts, Oliver and Romani, Roger W and Sgr{\`o}, Carmelo and Slane, Patrick and Spandre, Gloria and Swartz, Doug and Tamagawa, Toru and Tavecchio, Fabrizio and Taverna, Roberto and Tawara, Yuzuru and Tennant, Allyn F and Thomas, Nicholas E and Trois, Alessio and Turolla, Roberto and Vink, Jacco and Xie, Fei and Zane, Silvia},
        abstract = {The accretion of matter by compact objects can be inhibited by radiation pressure if the luminosity exceeds a critical value known as the Eddington limit. The discovery of ultraluminous X-ray sources has shown that accretion can proceed even when the apparent luminosity considerably exceeds this limit. A high apparent luminosity might be produced due to the geometric beaming of radiation by an outflow. The outflow half-opening angle, which determines the amplification due to beaming, has never been robustly constrained. Using the Imaging X-ray Polarimetry Explorer, we measured the X-ray polarization in the Galactic X-ray binary Cygnus X-3 (Cyg X-3). We found high, {\ensuremath{>}}20\%, nearly energy-independent linear polarization orthogonal to the direction of the radio ejections. These properties unambiguously indicate the presence of a collimating outflow from the X-ray binary Cyg X-3 and constrain its half-opening angle to {$\lesssim$}15o. Thus, the source can be used as a laboratory for studying the supercritical accretion regime. This finding underscores the importance of X-ray polarimetry in advancing our understanding of accreting sources.},
             url = {https://doi.org/10.1038/s41550-024-02294-9}
}