Tootfinder

XL-Calibur Polarimetry of Cyg X-1 Further Constrains the Origin of its Hard-state X-ray Emission
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, M\'ozsi Kiss, Kassi Klepper, Henric Krawczynski, Haruki Kuramoto, Lindsey Lisalda, Yoshitomo Maeda, Hironori Matsumoto, Shravan Vengalil Menon, Aiko Mi…

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^…