THE DIFFERENCE OF OPTICAL POLARIZATION PROPERTIES BETWEEN XBLs AND RBLs

On the basis of the beaming model, we have derived a relation between the observed polarization (P^ob) and Doppler-corrected optical magnitude (m^corr), log P^ob=0.4(1-k) m^corr+C. We tested the correlation between P^ob and m^corr. The main results are as follows: (1) for both high and low states, there are strong correlations between P^ob and m^corr for 29 RBLs with well-observed polarization and Doppler factor, where m^corr=m^ob+(3+\alpha)log\delta/0.4, and \delta is the optical Doppler factor; (2) no correlation exists between P^ob and the observed optical magnitude, m^ob, for the 29 RBLs in high state, but there is a close correlation for the 29 RBLs in low state; (3) however, there is an obvious anti-correlation between P^ob and m^corr for 35 XBLs with good simultaneous observation data. Our results show that (i) a new difference in polarization is found between RBLs and XBLs; (ii) this difference in polarization between RBLs and XBLs seems really to be physical differences.