Journal Article

Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE

Poutanen, Juri, Marshall, Herman L., O’Dell, Stephen L., Kislat, Fabian, Bright, Joe S., Kitaguchi, Takao, Papitto, Alessandro, Enoto, Teruaki, Oppedisano, Chiara, Latronico, Luca, Fabiani, Sergio, Ramsey, Brian D., Wu, Kinwah, Cavazzuti, Elisabetta, Heyl, Jeremy, Tsybulev, Peter, Veledina, Alexandra, Podgorný, Jakub, Petrucci, Pierre-Olivier, Mitsuishi, Ikuyuki, Lutovinov, Alexander A., Shevchenko, Anton, Xie, Fei, La Monaca, Fabio, Bursov, Nikolaj, Baumgartner, Wayne H., Ng, Chi-Yung, Liodakis, Ioannis, Muleri, Fabio, Piano, Giovanni, Tavecchio, Fabrizio, Marscher, Alan P., Matt, Giorgio, Swartz, Doug, Sgrò, Carmelo, Ferrazzoli, Riccardo, Gurwell, Mark, Tamagawa, Toru, Ehlert, Steven R., Perri, Matteo, Forsblom, Sofia V., Sunyaev, Rashid A., Pilia, Maura, Del Monte, Ettore, Krawczynski, Henric, Pavlov, George G., Roberts, Oliver, Baldini, Luca, Pesce-Rollins, Melissa, Turolla, Roberto, Rao, Ramprasad, Evangelista, Yuri, Di Marco, Alessandro, Di Lalla, Niccolò, Marin, Frédéric, Puccetti, Simonetta, Vink, Jacco, Costa, Enrico, McCollough, Michael, Kraus, Alex, Ingram, Adam, Ciprini, Stefano, Kajava, Jari J.

2024

Overview

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, >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 ≲15°. 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. The accretion geometry of X-ray binary Cygnus X-3 is determined here from IXPE observations. X-ray polarization reveals a narrow funnel with reflecting walls, which focuses emission, making Cyg X-3 appear as an ultraluminous X-ray source.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33/34/4118 / 639/33/34/864 / Astronomy / Astrophysics and Cosmology / Physics / Physics and Astronomy / Polarization / Radiation / Sciences of the Universe