Constraining the X-ray radiation origin of 3C 273 in the low state by polarization

Abstract

ABSTRACT 3C 273 is one of the nearest high-luminosity quasars. Although classified as a blazar, 3C 273 also has some features in Seyferts, whose X-ray may originate from the corona. Since both jet and corona produce power-law spectra in X-ray, the spectrum cannot completely distinguish their contributions to 3C 273 in the low state. X-ray polarimetric observations provide the chance to constrain the X-ray radiation origin of 3C 273 in the low state. We perform general relativistic radiative transfer simulations with the code monk to compute the X-ray polarization in 2–10 keV from the jets, sphere coronae, and slab coronae for 3C 273. We find that the radiation from the jet in 2–10 keV has a larger polarization degree than that of the corona: the polarization degree in 2–10 keV from the corona is unpolarized, while these are 4.1 per cent–15.8 per cent for the jet with a vertical or radial magnetic field and ≤5.0 per cent for the jet with toroidal magnetic field. The X-ray polarization of the corona and jet is sensitive to optical depth and geometry, and the main driver for this dependence is the number of scatterings. These results show that X-ray polarization can effectively constrain the X-ray radiation origin of 3C 273 in the low state.