X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator?

Mushtukov, Alexander A.; Tsygankov, Sergey S.; Poutanen, Juri; Doroshenko, V.; Salganik, Alexander; Costa, E.; Marco, Alessandro Di; Heyl, Jeremy; Monaca, Fabio La; Lutovinov, A.; A., Mereminsky, I.; Papitto, A.; Semena, A.; Shtykovsky, A. E.; Suleimanov, V.; Forsblom, Sofia V.; González–Caniulef, Denis; Malacaria, C.; Sunyaev, R.; Agudo, I.; Antonelli, L. A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, W. H.; Bellazzini, R.; Bianchi, S.; Bongiorno, Stephen D.; Bonino, R.; Brez, A.; Bucciantini, N.; Capitanio, Fiamma; Castellano, S; Cavazzuti, E.; Chen, Chun-Tao; Ciprini, S.; Rosa, A. De; Monte, E. Del; Gesu, Laura Di; Lalla, N. Di; Donnarumma, I.; Dovčiak, Michal; Ehlert, Steven R.; Enoto, T.; Evangelista, Y.; Fabiani, Sergio; Ferrazzoli, Riccardo; García, Javier A.; Gunji, Shuichi; Hayashida, Kentaro; Iwakiri, W.; Jorstad, Svetlana G.; Kaaret, Philip; Karas, V.; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, H.; Latronico, L.; Liodakis, Ioannis; Maldera, S.; Manfreda, Alberto; Marin, Frédéric; Marscher, A. P.; Marshall, Herman L.; Massaro, F.; Matt, Giorgio; Mitsuishi, Ikuyuki; Mizuno, T.; Muleri, Fabio; Negro, Michela; Ng, Chi-Yung; O’Dell, Stephen L.; Omodei, N.; Oppedisano, C.; Pavlov, G. G.; Peirson, Abel L.; Perri, M.; Pesce-Rollins, Melissa; Petrucci, P.-O.; Pilia, M.; Possenti, A.; Puccetti, S.; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Roberts, O. J.; Romani, Roger W.; Sgrò, C.; Slane, Patrick; Soffitta, P.; Spandre, G.; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, F.; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, A.; Turolla, R.; Vink, Jacco; Weisskopf, Martin C.; Wu, Kinwah; Xie, Fei; Zane, S.

doi:10.1093/mnras/stad1961

Cited by 15 publications

(1 citation statement)

References 54 publications

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“…The Imaging X-ray Polarimetry Explorer (IXPE; Weisskopf et al 2022) provides a unique opportunity to probe the X-ray polarization of XRPs. So far, the detection of phase-averaged/ resolved polarized emission in a handful of XRPs, such as Her X−1 (∼10%; Doroshenko et al 2022), Cen X−3 (∼5.8%; Tsygankov et al 2022), 4U 1626 − 67 (∼4.8%; Marshall et al 2022), Vela X−1 (∼2.3%; Forsblom et al 2023), GRO J1008 − 57 (∼15%; Tsygankov et al 2023), EXO 2030 + 375 (∼3%; Malacaria et al 2023), X Persei (∼20%; Mushtukov et al 2023), and GX 301 − 2 (∼3%-10%; Suleimanov et al 2023) is confirmed with IXPE. If not all, most of the sources show a "low" polarization degree (PD) compared to the predictions from the existing models (Meszaros et al 1988;Caiazzo & Heyl 2021a, 2021b, and its cause remains an open question to date.…”

Section: Introductionmentioning

confidence: 99%

First Detection of X-Ray Polarization in Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 with IXPE

Majumder,

Chatterjee,

Jayasurya

et al. 2024

ApJL

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We report the results of first ever spectropolarimetric analyses of the Galactic ultraluminous X-ray pulsar Swift J0243.6+6124 during the 2023 outburst using quasi-simultaneous IXPE, NICER, and NuSTAR observations. A pulsation of period ∼9.79 s is detected in IXPE and NuSTAR observations with pulse fractions (PFs) ∼18% (2–8 keV) and ∼28% (3–78 keV), respectively. Energy-dependent study of the pulse profiles with NuSTAR indicates an increase in PF from ∼27% (3–10 keV) to ∼50% (40–78 keV). Further, epoch-dependent polarimetric measurements during the decay phase of the outburst confirm the detection of significant polarization, with the polarization degree (PD) and polarization angle ranging between ∼2%–3.1% and ∼8.°6–10.°8, respectively, in the 2–8 keV energy range. We also observe that the PD increases up to ∼4.8% at higher energies (≳5 keV) with dominating bbodyrad flux contribution (1.5 ≲ F BB/F PL ≲ 3.4) in the IXPE spectra. The phase-resolved polarimetric study yields PD as ∼1.7%–3.1% suggesting a marginal correlation with the pulse profiles. Moreover, the broadband (0.6–70 keV) energy spectrum of combined NICER and NuSTAR observations is well described by the combination of bbodyrad and cutoffpl components with seed photon temperature (kT bb) ∼0.86 ± 0.03 keV and photon index (Γ) ∼0.98 ± 0.01. With the above findings, we infer that the observed “low” PD in Swift J0243.6+6124 is attributed possibly due to the “vacuum resonance” effect between the overheated and relatively cooler regions of the neutron star boundary layer.

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Section: Introductionmentioning

confidence: 99%

First Detection of X-Ray Polarization in Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 with IXPE

Majumder,

Chatterjee,

Jayasurya

et al. 2024

ApJL

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X-ray polarimetry of the accreting pulsar GX 301−2

Suleimanov,

Forsblom,

Tsygankov

et al. 2023

A&A

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The phase- and energy-resolved polarization measurements of accreting X-ray pulsars (XRPs) allow us to test different theoretical models of their emission, and they also provide an avenue to determine the emission region geometry. We present the results of the observations of the XRP GX 301−2 performed with the Imaging X-ray Polarimetry Explorer (IXPE). A persistent XRP, GX 301−2 has one of the longest spin periods known: ∼680 s. A massive hyper-giant companion star Wray 977 supplies mass to the neutron star via powerful stellar winds. We did not detect significant polarization in the phase-averaged data when using spectro-polarimetric analysis, with the upper limit on the polarization degree (PD) of 2.3% (99% confidence level). Using the phase-resolved spectro-polarimetric analysis, we obtained a significant detection of polarization (above 99% confidence level) in two out of nine phase bins and a marginal detection in three bins, with a PD ranging between ∼3% and ∼10% and a polarization angle varying in a very wide range from ∼0° to ∼160°. Using the rotating vector model, we obtained constraints on the pulsar geometry using both phase-binned and unbinned analyses, finding excellent agreement. Finally, we discuss possible reasons for a low observed polarization in GX 301−2.

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Complex variations in X-ray polarization in the X-ray pulsar LS V +44 17/RX J0440.9+4431

Doroshenko¹,

Poutanen²,

Heyl³

et al. 2023

A&A

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We report on Imaging X-ray polarimetry explorer (IXPE) observations of the Be-transient X-ray pulsar LS V +44 17/RX J0440.9+4431 made at two luminosity levels during the giant outburst in January–February 2023. Considering the observed spectral variability and changes in the pulse profiles, the source was likely caught in supercritical and subcritical states with significantly different emission-region geometry, associated with the presence of accretion columns and hot spots, respectively. We focus here on the pulse-phase-resolved polarimetric analysis and find that the observed dependencies of the polarization degree and polarization angle (PA) on the pulse phase are indeed drastically different for the two observations. The observed differences, if interpreted within the framework of the rotating vector model (RVM), imply dramatic variations in the spin axis inclination, the position angle, and the magnetic colatitude by tens of degrees within the space of just a few days. We suggest that the apparent changes in the observed PA phase dependence are predominantly related to the presence of an unpulsed polarized component in addition to the polarized radiation associated with the pulsar itself. We then show that the observed PA phase dependence in both observations can be explained with a single set of RVM parameters defining the pulsar’s geometry. We also suggest that the additional polarized component is likely produced by scattering of the pulsar radiation in the equatorial disk wind.

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X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator?

Cited by 15 publications

References 54 publications

First Detection of X-Ray Polarization in Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 with IXPE

First Detection of X-Ray Polarization in Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 with IXPE

X-ray polarimetry of the accreting pulsar GX 301−2

Complex variations in X-ray polarization in the X-ray pulsar LS V +44 17/RX J0440.9+4431

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