2006ApJ...648L..59V

Water maser polarization observations in the precessing jet of W43A have revealed that it is magnetically collimated. Here we present a detailed description of the physical properties of the water maser environment in the jet. We discuss the maser saturation level and beaming angle as well as the intrinsic temperatures and densities. In addition, we show that the polarization angle of the strongest redshifted maser feature undergoes a fast rotation of 90° across the maser. Along with the variation of linear polarization fraction, this strongly supports the current theoretical description of maser linear polarization.