학술논문
First detection of X-ray polarization from the accreting neutron star 4U 1820-303
Document Type
Working Paper
Author
Di Marco, Alessandro; La Monaca, Fabio; Poutanen, Juri; Russell, Thomas D.; Anitra, Alessio; Farinelli, Ruben; Mastroserio, Guglielmo; Muleri, Fabio; Xie, Fei; Bachetti, Matteo; Burderi, Luciano; Carotenuto, Francesco; Del Santo, Melania; Di Salvo, Tiziana; Dovciak, Michal; Gnarini, Andrea; Iaria, Rosario; Kajava, Jari J. E.; Liu, Kuan; Middei, Riccardo; O'Dell, Stephen L.; Pilia, Maura; Rankin, John; Sanna, Andrea; Eijnden, Jakob van den; Weisskopf, Martin C.; Bobrikova, Anna; Capitanio, Fiamma; Costa, Enrico; Kaaret, Philip; Marino, Alessio; Soffitta, Paolo; Ursini, Francesco; Ambrosino, Filippo; Cocchi, Massimo; Fabiani, Sergio; Marshall, Herman L.; Matt, Giorgio; Motta, Sara Elisa; Papitto, Alessandro; Stella, Luigi; Tarana, Antonella; Zane, Silvia; Agudo, Ivan; Antonelli, Lucio A.; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolo; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccolo; Donnarumma, Immacolata; Doroshenko, Victor; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; 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, Frederic; Marinucci, Andrea; Marscher, Alan P.; Massaro, Francesco; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Negro, Michela; Ng, Chi-Yung; 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; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Wu, Kinwah
Source
ApJL 953 L22 (2023)
Subject
Language
Abstract
This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820-303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with the Australia Telescope Compact Array (ATCA). The IXPE observations of 4U 1820-303 were coordinated with Swift-XRT, NICER, and NuSTAR aiming to obtain an accurate X-ray spectral model covering a broad energy interval. The source shows a significant polarization above 4 keV, with a polarization degree of 2.0(0.5)% and a polarization angle of -55(7) deg in the 4-7 keV energy range, and a polarization degree of 10(2)% and a polarization angle of -67(7) deg in the 7-8 keV energy bin. This polarization also shows a clear energy trend with polarization degree increasing with energy and a hint for a position-angle change of about 90 deg at 96% CL around 4 keV. The spectro-polarimetric fit indicates that the accretion disk is polarized orthogonally to the hard spectral component, which is presumably produced in the boundary/spreading layer. We do not detect linear polarization from the radio counterpart, with a 99.97% upper limit of 50% at 7.25 GHz.