Fermi Gamma-ray Space Telescope

Multi-epoch quasi-simultaneous SEDs of southern blazars

F.
J. Trstedt, C. Mller, B. Carpenter, R. Schulz, A. Kreikenbohm, K. Leiter, T. Beuchert, M. Langejahn, M. Oertel, M. Kadler, R. Ojha, J. Wilms, for the TANAMI collaboration, S. Buson, for the LAT collaboration

Abstract:

Within the framework of the TANAMI and the EXTraS projects, we study the dynamic spectral energy distributions of 22 southern blazars. Using a Bayesian block algorithm on Fermi-LAT light curves we determine source states of constant flux. We use time periods in which X-ray and VLBI data are also available to construct a total of 80 quasi-simultaneous SEDs. We fit the data in detector space with two logarithmic parabolas to describe the two peaks, as well as the absorption model and corresponding extinction. We find that the high-energy peak frequency generally follows the blazar sequence for low and intermediate source states. For high flux states and gamma-ray flares, there are indications that the correlation is inverted in the sense that the most luminous flares seem to peak at the highest energies. Our approach allows us to further study relations between important physical quantities such as the Compton dominance as a function of source activity state. It also lets us explore the dependence of the X-ray - radio connection on the source activity state. We further compare the black hole mass as predicted by the fundamental plane with measurements in the literature.