Title: | X-Ray Polarized View of the Accretion Geometry in the X-Ray Binary Circinus X-1 |
Authors: | RANKIN, John LA MONACA, Fabio DI MARCO, Alessandro Poutanen, Juri Bobrikova, Anna Kravtsov, Vadim MULERI, FABIO PILIA, Maura Veledina, Alexandra Fender, Rob Kaaret, Philip TROIS, ALESSIO Turolla, Roberto Vink, Jacco XIE, FEI Kim, Dawoon E. Marinucci, Andrea Marshall, Herman L. PAPITTO, ALESSANDRO Tennant, Allyn F. Tsygankov, Sergey S. Weisskopf, Martin C. Wu, Kinwah Zane, Silvia AMBROSINO, Filippo FARINELLI, Ruben Gnarini, Andrea Agudo, Iván ANTONELLI, Lucio Angelo BACHETTI, Matteo Baldini, Luca Baumgartner, Wayne H. Bellazzini, Ronaldo Bianchi, Stefano Bongiorno, Stephen D. Bonino, Raffaella Brez, Alessandro BUCCIANTINI, Niccolo' CAPITANIO, FIAMMA Castellano, Simone Cavazzuti, Elisabetta Chen, Chien-Ting Ciprini, Stefano COSTA, ENRICO DE ROSA, Alessandra DEL MONTE, Ettore Di Gesu, Laura Di Lalla, Niccolò Donnarumma, Immacolata Doroshenko, Victor Dovčiak, Michal Ehlert, Steven R. Enoto, Teruaki EVANGELISTA, YURI FABIANI, Sergio FERRAZZOLI, RICCARDO Garcia, Javier A. Gunji, Shuichi Hayashida, Kiyoshi Heyl, Jeremy Iwakiri, Wataru Jorstad, Svetlana G. Karas, Vladimir Kislat, Fabian Kitaguchi, Takao Kolodziejczak, Jeffery J. Krawczynski, Henric Latronico, Luca Liodakis, Ioannis Maldera, Simone Manfreda, Alberto Marin, Frédéric Marscher, Alan P. MASSARO, FRANCESCO Matt, Giorgio Mitsuishi, Ikuyuki Mizuno, Tsunefumi Negro, Michela Ng, Chi-Yung O'Dell, Stephen L. Omodei, Nicola Oppedisano, Chiara Pavlov, George G. Peirson, Abel L. PERRI, Matteo Pesce-Rollins, Melissa Petrucci, Pierre-Olivier POSSENTI, ANDREA Puccetti, Simonetta Ramsey, Brian D. RATHEESH, AJAY Roberts, Oliver J. Romani, Roger W. Sgrò, Carmelo Slane, Patrick SOFFITTA, PAOLO Spandre, Gloria Swartz, Douglas A. Tamagawa, Toru TAVECCHIO, Fabrizio Taverna, Roberto Tawara, Yuzuru Thomas, Nicholas E. TOMBESI, Francesco |
Issue Date: | 2024 |
Journal: | THE ASTROPHYSICAL JOURNAL LETTERS |
Number: | 961 |
Issue: | 1 |
First Page: | L8 |
Abstract: | Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ~16.6 day orbit. There are also strong variations in the spectral state, and it has historically shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263 ks. We find an X-ray polarization degree in these segments of 1.6% ± 0.3% and 1.4% ± 0.3% at polarization angles of 37° ± 5° and -12° ± 7°, respectively. Thus, we observed a rotation of the polarization angle by 49° ± 8° along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio and found the polarization angle differing by 67° ± 11° between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star's angular momentum with respect to the orbital one. |
URI: | http://hdl.handle.net/20.500.12386/34824 |
URL: | https://iopscience.iop.org/article/10.3847/2041-8213/ad1832 https://api.elsevier.com/content/abstract/scopus_id/85182584553 |
ISSN: | 2041-8205 |
DOI: | 10.3847/2041-8213/ad1832 |
Bibcode ADS: | 2024ApJ...961L...8R |
Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista
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