A1 Refereed original research article in a scientific journal
Observations of 4U 1626-67 with the Imaging X-Ray Polarimetry Explorer
Authors: Marshall Herman L., Ng Mason, Rogantini Daniele, Heyl Jeremy, Tsygankov Sergey S., Poutanen Juri, Costa Enrico, Zane Silvia, Malacaria Christian, Agudo Iván, Antonelli Lucio A., Bachetti Matteo, Baldini Luca, Baumgartner Wayne H., Bellazzini Ronaldo, Bianchi Stefano, Bongiorno Stephen D., Bonino Raffaella, Brez Alessandro, Bucciantini Niccolò, Capitanio Fiamma, Castellano Simone, Cavazzuti Elisabetta, Ciprini Stefano, De Rosa Alessandra, Monte Ettore Del, Gesu Laura Di, Lalla Niccolò Di, Marco Alessandro Di, Donnarumma Immacolata, Doroshenko Victor, Dovčiak Michal, Ehlert Steven R., Enoto Teruaki, Evangelista Yuri, Fabiani Sergio, Ferrazzoli Riccardo, Garcia Javier A., Gunji Shuichi, Hayashida Kiyoshi, Iwakiri Wataru, Jorstad Svetlana G., Karas Vladimir, Kitaguchi Takao, Kolodziejczak Jeffery J., Krawczynski Henric, Monaca Fabio La, Latronico Luca, Liodakis Ioannis, Maldera Simone, Manfreda Alberto, Marin Frédéric, Marinucci Andrea, Marscher Alan P., Matt Giorgio, Mitsuishi Ikuyuki, Mizuno Tsunefumi, Muleri Fabio, Ng C.-Y., O'Dell Stephen L., Omodei Nicola, Oppedisano Chiara, Papitto Alessandro, Pavlov George G., Peirson Abel L., Perri Matteo, Pesce-Rollins Melissa, Petrucci Pierre-Olivier, Pilia Maura, Possenti Andrea, Puccetti Simonetta, Ramsey Brian D., Rankin John, Ratheesh Ajay, Romani Roger W., Sgrò Carmelo, Slane Patrick, Soffitta Paolo, Spandre Gloria, Tamagawa Toru, Tavecchio Fabrizio, Taverna Roberto, Tawara Yuzuru, Tennant Allyn F., Thomas Nicholas E., Tombesi Francesco, Trois Alessio, Turolla Roberto, Vink Jacco, Weisskopf Martin C., Wu Kinwah, Xie Fei, (IXPE Collaboration), Schulz Norbert S., Chakrabarty Deepto
Publisher: IOP Publishing
Publication year: 2022
Journal: Astrophysical Journal
Journal name in source: Astrophysical Journal
Article number: 70
Volume: 940
Issue: 1
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ac98c2
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ac98c2
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/177970437
We present measurements of the polarization of X-rays in the 2–8 keV band from the pulsar in the ultracompact low-mass X-ray binary 4U 1626–67 using data from the Imaging X-Ray Polarimetry Explorer (IXPE). The 7.66 s pulsations were clearly detected throughout the IXPE observations as well as in the NICER soft X-ray observations, which we used as the basis for our timing analysis and to constrain the spectral shape over the 0.4–10 keV energy band. Chandra HETGS high-resolution X-ray spectra were also obtained near the times of the IXPE observations for firm spectral modeling. We found an upper limit on the pulse-averaged linear polarization of <4% (at 95% confidence). Similarly, there was no significant detection of polarized flux in pulse phase intervals when subdividing the bandpass by energy. However, spectropolarimetric modeling over the full bandpass in pulse phase intervals provided a marginal detection of polarization of the power-law spectral component at the 4.8% ± 2.3% level (90% confidence). We discuss the implications concerning the accretion geometry onto the pulsar, favoring two-component models of the pulsed emission.
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