IMPLICATIONS FOR THE BLAZAR SEQUENCE AND INVERSE COMPTON MODELS FROM<i>FERMI</i>BRIGHT BLAZARS

Abstract

In this paper, we use the quasi-simultaneous spectra of Fermi bright blazars\nand Fermi detected narrow line Seyfert 1 (NLS1) to study the blazar sequence\nand inverse Compton (IC) models. I. The synchrotron peak luminosities (L_{s})\nsignificantly inverse correlate with the synchrotron peak frequencies\n(\\nu_{s}), L_{s}\\propto\\nu_{s}^{-0.44}, which is consistent with the blazar\nsequence. In addition to the correlation, there are some blazars showing low\n\\nu_{s} and low L_{s}. To study the relation between these low \\nu_{s} low\nL_{s} blazars and the blazar sequence, we present correlations of the parameter\nL_{s}\\nu_{s}^{1/4} with the ratio of Compton to synchrotron peak frequencies\n(r_{Cs}\\equiv\\nu_{C}/\\nu_{s}) and with the ratio of Compton to synchrotron\nluminosities (CD\\equiv L_{C}/L_{s}). The results indicate that both\ncorrelations are significant with a Pearson's probability for null correlation\nof p=0.0218 and p=0.0286 respectively. This does not support the idea that the\nlow \\nu_{s} low L_{s} blazars are sources with less beaming. Another\npossibility, as suggested by Ghisellini &amp; Tavecchio, is that these blazars have\nrelative lower black hole masses. To test this, we collect the black hole\nmasses of 30 blazars from archives, and find that the hole mass correlates with\nthe parameter L_{s}\\nu_{s}^{0.44} (p=0.0344). Therefore, the black hole masses\nof low \\nu_{s} low L_{s} blazars are statistically small. The NLS1s are thought\nto have lower black hole masses. We find that the four NLS1s detected by Fermi\nhave low \\nu_{s} and low L_{s}. This supports the above result. II. The ratio\nr_{Cs} correlates with CD significantly (p=0.00375). The external Compton (EC)\nmodel can naturally explain this correlation, while synchrotron self Compton\n(SSC) model can not. This agrees with the findings of many authors that the EC\nprocess dominates the gamma-ray emission of Flat Spectrum Radio Quasars.\n