Kavli Affiliate: Grzegorz Madejski
| Summary:
Observations of linear polarization in the 2-8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating non-thermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy particles within the jet. IXPE observations of the X-ray selected BL Lac-type blazar 1ES 1959+650 in 2022 May 3-4 showed a significant linear polarization degree of $Π_mathrmx = 8.0% pm 2.3%$ at an electric-vector position angle $ψ_mathrmx = 123^circ pm 8^circ$. However, in 2022 June 9-12, only an upper limit of $Π_mathrmx leq 5.1%$ could be derived (at the 99% confidence level). The degree of optical polarization at that time $Π_mathrmO sim 5%$ is comparable to the X-ray measurement. We investigate possible scenarios for these findings, including temporal and geometrical depolarization effects. Unlike some other X-ray selected BL Lac objects, there is no significant chromatic dependence of the measured polarization in 1ES 1959+650, and its low X-ray polarization may be attributed to turbulence in the jet flow with dynamical timescales shorter than 1 day.
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