X-ray Spectral Properties for Blazars

A sample including 69 blazars is selected from the literature.Using the sample,the relations between the flux density and spectral index,the distributions of redshift and spectral index are investigated for the high frequency peaked BL Lac objects(HBLs),lowly frequency peaked BL Lac object(LBLs) and the flat spectral radio quasars(FSRQs) respectively.Our results show that(1) an anti-correlation is found between the spectral index and the flux density for HBLs,but there is no clear relations for LBLs or FSRQs,which suggest that the X-ray emission in HBLs are from the synchrotron process while that for LBLs and FSRQs from the synchrotron self-Compton process,(2) the X-ray spectral index has a consequence for the three subclasses with HBLs showing the softest X-ray spectral,and FSRQs,the hardest X-ray spectrum and LBLs being between them,and(3) HBLs locate at the nearest while FSRQs the furthest and LBLs being between them.