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 \(\Pi _X = 9.0 \pm 1.6\) ${\mathrm{\Pi }}_X=9.0\pm 1.6$ % and an electric vector position angle of \(\Psi _X = 53 \pm 5\) ${\mathrm{\Psi }}_X=53\pm 5$ deg. Similarly, from the observations on 14 August 2023, we found \(\Pi _X\) ${\mathrm{\Pi }}_X$ and \(\psi _X\) ${\psi }_X$ values as \(12.5 \pm 0.7\) $12.5\pm 0.7$ % and \(20 \pm 2\) $20\pm 2$ 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 ( \(\Gamma \) $\mathrm{\Gamma }$ ) 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 \(\Pi _X\) ${\mathrm{\Pi }}_X$ between the two epochs being influenced by a change in the \(\Gamma \) $\mathrm{\Gamma }$ of the jet.