The long and short timescale polarization variability of the BL Lacertae object PKS 0109+224.

This paper presents fifteen new simultaneous UBVRI photopolarimetric observations of the BL Lac object PKS 109+224. The data include night to night observations and four long intranight integrations. All the possible correlations between the flux, polarization and position angle in the five colors are presented for different timescales. The analysis of the long time behavior of the source includes all the existing data of the object. The results are discussed in the context of shock models. According to the data it seems that the short and long timescale variations are due to different processes.