XL-Calibur Polarimetry of Cyg X-1 Further Constrains the Origin of its Hard-state X-ray Emission
XL-Calibur Polarimetry of Cyg X-1 Further Constrains the Origin of its Hard-state X-ray Emission
The balloon-borne hard X-ray polarimetry mission XL-Calibur observed the Black Hole X-ray Binary (BHXRB) Cygnus X-1 (Cyg X-1) during its nearly six-day Long Duration Balloon (LDB) flight from Sweden to Canada in July 2024. The XL-Calibur observations allowed us to derive the most precise constraints to date of the Polarization Degree (PD) and Polarization Angle (PA) of the hard X-ray emission from a BHXRB. XL-Calibur observed Cyg X-1 in the hard state and measured a $\sim$19-64 keV PD of ($5.0^{+2.7}_{-3.0}$)% at a PA of $-28^{\circ}\pm 17^{\circ}$, with an 8.7% chance probability of detecting larger PDs than the one observed, given an unpolarized signal. The XL-Calibur results are thus comparable to the 2-8 keV PD and PA found by IXPE, with a similar agreement between the hard X-ray PA and the radio jet direction. We also discuss the implications of our polarization measurements in the context of models describing the origin of the broadband X-ray and $γ$-ray emission, to which XL-Calibur provides independent constraints on any proposed emission modeling.
Hisamitsu Awaki、Matthew G. Baring、Richard Bose、Jacob Casey、Sohee Chun、Adrika Dasgupta、Pavel Galchenko、Ephraim Gau、Kazuho Goya、Tomohiro Hakamata、Takayuki Hayashi、Scott Heatwole、Kun Hu、Daiki Ishi、Manabu Ishida、Fabian Kislat、Mózsi Kiss、Kassi Klepper、Henric Krawczynski、Haruki Kuramoto、Lindsey Lisalda、Yoshitomo Maeda、Hironori Matsumoto、Shravan Vengalil Menon、Aiko Miyamoto、Asca Miyamoto、Kaito Murakami、Takashi Okajima、Mark Pearce、Brian Rauch、Nicole Rodriguez Cavero、Kentaro Shirahama、Sean Spooner、Hiromitsu Takahashi、Keisuke Tamura、Yuusuke Uchida、Kasun Wimalasena、Masato Yokota、Marina Yoshimoto
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Hisamitsu Awaki,Matthew G. Baring,Richard Bose,Jacob Casey,Sohee Chun,Adrika Dasgupta,Pavel Galchenko,Ephraim Gau,Kazuho Goya,Tomohiro Hakamata,Takayuki Hayashi,Scott Heatwole,Kun Hu,Daiki Ishi,Manabu Ishida,Fabian Kislat,Mózsi Kiss,Kassi Klepper,Henric Krawczynski,Haruki Kuramoto,Lindsey Lisalda,Yoshitomo Maeda,Hironori Matsumoto,Shravan Vengalil Menon,Aiko Miyamoto,Asca Miyamoto,Kaito Murakami,Takashi Okajima,Mark Pearce,Brian Rauch,Nicole Rodriguez Cavero,Kentaro Shirahama,Sean Spooner,Hiromitsu Takahashi,Keisuke Tamura,Yuusuke Uchida,Kasun Wimalasena,Masato Yokota,Marina Yoshimoto.XL-Calibur Polarimetry of Cyg X-1 Further Constrains the Origin of its Hard-state X-ray Emission[EB/OL].(2025-07-30)[2025-08-07].https://arxiv.org/abs/2507.23126.点此复制
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