Detection of X-ray polarization in the high synchrotron peaked blazar 1ES 1959+650.

We report the measurement of X-ray polarization in the high synchrotron peaked blazar 1ES 1959 + 650. Of the four epochs of observations from the Imaging X-ray Polarimetry Explorer, we detected polarization in the 2–8 keV band on two epochs. From the model-independent analysis of the observations on 28 October 2022, in the 2–8 keV band, we found the degree of polarization of Π X = 9.0 ± 1.6 % and an electric vector position angle of Ψ X = 53 ± 5 deg. Similarly, from the observations on 14 August 2023, we found Π X and ψ X values as 12.5 ± 0.7 % and 20 ± 2 deg, respectively. These values are also in agreement with the values obtained from spectro-polarimetric analysis of the I, Q, and U spectra. The measured X-ray polarization is larger than the reported optical values, ranging between 2.5% and 9% when observed from 2008 to 2018. Broadband spectral energy distribution constructed for the two epochs is well described by the one-zone leptonic emission model with the bulk Lorentz factor (Γ ) of the jet larger on 14 August 2023 compared to 28 October 2022. Our results favor the shock acceleration of the particles in the jet, with the difference in Π X between the two epochs being influenced by a change in the Γ of the jet. [ABSTRACT FROM AUTHOR]