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20242026
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astro-ph.HE2026

Energy-Resolved Limits on Orbital X-ray Polarization Modulation in Cygnus X-1

Sohee Chun, Bert Vander Meulen, Kun Hu +1

Reflection off the companion star and its focused stellar wind is predicted to modulate the X-ray polarization of black hole X-ray binaries at half the orbital period ($P_{\rm orb}…

astro-ph.HE2026

Refined Constraints on the Hard X-ray Polarization of the Crab Pulsar and Nebula Derived from an Extended XL-Calibur Dataset

Matthew G. Baring, Jacob Casey, Sohee Chun +26

We present updated hard X-ray polarization measurements of the Crab pulsar and nebula obtained with the balloon-borne polarimeter XL-Calibur in the ~19-64 keV energy range. During…

astro-ph.HE2025

XL-Calibur measurements of polarised hard X-ray emission from the Crab

Hisamitsu Awaki, Matthew G. Baring, Richard Bose +46

We report measurements of the linear polarisation degree (PD) and angle (PA) for hard X-ray emission from the Crab pulsar and wind nebula. Measurements were made with the XL-Calibu…

astro-ph.HE2025

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 +36

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)…

astro-ph.HE2024

Evaluation of several explanations of the strong X-ray polarization of the black hole X-ray binary 4U 1630-47

Henric Krawczynski, Yajie Yuan, Alexander Y. Chen +6

The Imaging X-ray Polarimetry Explorer (IXPE) observations of the X-ray binary 4U 1630-47 in the high soft state revealed high linear polarization degrees (PDs) rising from 6% at 2…

astro-ph.HE2024

An IXPE-Led X-ray Spectro-Polarimetric Campaign on the Soft State of Cygnus X-1: X-ray Polarimetric Evidence for Strong Gravitational Lensing

James F. Steiner, Edward Nathan, Kun Hu +134

We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwav…