2025/12/10 by Hu, Xin-Ke, Zhang, Jin, Xie, Fei +1
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2512.09448
We present the first X-ray polarimetric observation of the extreme high-synchrotron-peaked blazar 1ES 1101--232, conducted by the Imaging X-ray Polarimetry Explorer (IXPE). The data analysis incorporates simultaneous and quasi-simultaneous observations from Swift-XRT and NuSTAR. Our results reveal a significant detection of X-ray polarization in the 2--6 keV band at a confidence level (CL) of 6.6σ, with a polarization degree of Π\rm X=17.9%±2.7% and an electric vector position angle (EVPA) of ψ\rm X=10^∘.0±4^∘.4. An even higher polarization degree of Π\rm X=38.9%±9.1% with an EVPA of ψ\rm X=13^∘.9±6^∘.7 is observed within a narrower time interval, at a CL of 4.3σ. During the IXPE observational campaign, the X-ray spectrum of 1ES 1101--232 exhibits a clear soft-to-hard spectral evolution in the 0.3--10 keV band, although no significant flux variability is detected. Additionally, a clockwise hysteresis loop is identified in the flux--photon index plane. These findings collectively indicate that the X-ray emission from 1ES 1101--232 originates in a region characterized by a well-ordered magnetic field through synchrotron radiation.