Blazar 4C+01.02 opt. LCO phot. & SALT spectropol.

The unpolarized radiation components from the AD, BLR, and host galaxy present themselves by decreasing the total polarization in the optical/ultraviolet (UV) spectrum. A combined model for the spectral energy distribution (SED) and degree of optical/UV polarization is constructed, enabling the disentanglement of the synchrotron and AD components.

Our model is applied to the multiwavelength SED and spectropolarimetry observations of the flat-spectrum radio quasar 4C+01.02 (z=2.1) in its 2016 July-August flaring state and 2017 July-August quiescent state, using data from the Fermi Large Area Telescope, the Southern African Large Telescope, and the Las Cumbres Observatory network of telescopes. By constraining the AD component, the mass of the supermassive black hole is obtained as ~3x10^9^M_{sun}_.