The difference of optical polarization properties between XBLs and RBLs

On the basis of the beaming model, we have derived a relation between the o bserved 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-o b and m(corr). The main results are as follows: (1) for both high and low s tates, there are strong correlations between P-ob and m(corr) for 29 RBLs w ith 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 betwe en P-ob and m(corr) for 35 XBLs with good simultaneous observation data. Ou r results show that (i) a new difference in polarization is found between R BLs and XBLs; (ii) this difference in polarization between RBLs and XBLs se ems really to be physical differences.