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Published December 2022 | public
Journal Article

Determination of X-ray pulsar geometry with IXPE polarimetry

Doroshenko, Victor ORCID icon
Poutanen, Juri ORCID icon
Tsygankov, Sergey S. ORCID icon
Suleimanov, Valery F. ORCID icon
Bachetti, Matteo ORCID icon
Caiazzo, Ilaria ORCID icon
Costa, Enrico ORCID icon
Di Marco, Alessandro ORCID icon
Heyl, Jeremy ORCID icon
La Monaca, Fabio ORCID icon
Muleri, Fabio ORCID icon
Mushtukov, Alexander A.
Pavlov, George G. ORCID icon
Ramsey, Brian D.
Rankin, John ORCID icon
Santangelo, Andrea ORCID icon
Soffitta, Paolo ORCID icon
Staubert, Rüdiger ORCID icon
Weisskopf, Martin C. ORCID icon
Zane, Silvia
Agudo, Iván ORCID icon
Antonelli, Lucio A.
Baldini, Luca ORCID icon
Baumgartner, Wayne H.
Bellazzini, Ronaldo ORCID icon
Bianchi, Stefano ORCID icon
Bongiorno, Stephen D.
Bonino, Raffaella ORCID icon
Brez, Alessandro
Bucciantini, Niccolò ORCID icon
Capitanio, Fiamma ORCID icon
Castellano, Simone ORCID icon
Cavazzuti, Elisabetta ORCID icon
Ciprini, Stefano ORCID icon
De Rosa, Alessandra ORCID icon
Del Monte, Ettore ORCID icon
Di Gesu, Laura
Di Lalla, Niccolò ORCID icon
Donnarumma, Immacolata ORCID icon
Dovčiak, Michal ORCID icon
Ehlert, Steven R. ORCID icon
Enoto, Teruaki ORCID icon
Evangelista, Yuri ORCID icon
Fabiani, Sergio ORCID icon
Ferrazzoli, Riccardo ORCID icon
García, Javier A. ORCID icon
Gunji, Shuichi ORCID icon
Hayashida, Kiyoshi
Iwakiri, Wataru ORCID icon
Jorstad, Svetlana G. ORCID icon
Karas, Vladimir ORCID icon
Kitaguchi, Takao
Kolodziejczak, Jeffery J.
Krawczynski, Henric ORCID icon
Latronico, Luca ORCID icon
Liodakis, Ioannis ORCID icon
Maldera, Simone ORCID icon
Manfreda, Alberto ORCID icon
Marin, Frédéric ORCID icon
Marinucci, Andrea ORCID icon
Marscher, Alan P. ORCID icon
Marshall, Herman L. ORCID icon
Matt, Giorgio ORCID icon
Mitsuishi, Ikuyuki
Mizuno, Tsunefumi ORCID icon
Ng, Chi-Yung ORCID icon
O'Dell, Stephen L. ORCID icon
Omodei, Nicola ORCID icon
Oppedisano, Chiara ORCID icon
Papitto, Alessandro ORCID icon
Peirson, Abel L. ORCID icon
Perri, Matteo ORCID icon
Pesce-Rollins, Melissa ORCID icon
Pilia, Maura ORCID icon
Possenti, Andrea ORCID icon
Puccetti, Simonetta ORCID icon
Ratheesh, Ajay
Romani, Roger W. ORCID icon
Sgrò, Carmelo ORCID icon
Slane, Patrick ORCID icon
Spandre, Gloria ORCID icon
Sunyaev, Rashid A.
Tamagawa, Toru ORCID icon
Tavecchio, Fabrizio ORCID icon
Taverna, Roberto ORCID icon
Tawara, Yuzuru
Tennant, Allyn F.
Thomas, Nicolas E.
Tombesi, Francesco ORCID icon
Trois, Alessio ORCID icon
Turolla, Roberto ORCID icon
Vink, Jacco ORCID icon
Wu, Kinwah
Xie, Fei

Abstract

Using observations of X-ray pulsar Hercules X-1 by the Imaging X-ray Polarimetry Explorer we report a highly significant (>17σ) detection of the polarization signal from an accreting neutron star. The observed degree of linear polarization of ~10% is far below theoretical expectations for this object, and stays low throughout the spin cycle of the pulsar. Both the degree and angle of polarization exhibit variability with the pulse phase, allowing us to measure the pulsar spin position angle 57(2) deg and the magnetic obliquity 12(4) deg, which is an essential step towards detailed modelling of the intrinsic emission of X-ray pulsars. Combining our results with the optical polarimetric data, we find that the spin axis of the neutron star and the angular momentum of the binary orbit are misaligned by at least ~20 deg, which is a strong argument in support of the models explaining the stability of the observed superorbital variability with the precession of the neutron star.

Additional Information

This Article is based on observations made by IXPE, a joint US and Italian mission. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at the NASA Goddard Space Flight Center (GSFC). The US contribution is supported by NASA and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract number NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract number ASI-OHBI-2017-12-I.0, agreement numbers ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. V.D. and V.F.S. acknowledge support from the German Academic Exchange Service (DAAD) under travel grant number 57525212. J.P. and S.S.T. thank the Russian Science Foundation for support under grant number 20-12-00364 and the Academy of Finland for support under grant numbers 333112, 349144, 349373 and 349906. V.F.S. thanks the German Research Foundation (DFG) for grant number WE 1312/53-1. I.C. is a Sherman Fairchild Fellow at Caltech and thanks the Burke Institute at Caltech for supporting her research. A.A.M. acknowledges support from the Netherlands Organization for Scientific Research Veni Fellowship.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023