Poster Open Access

Optical-Gamma-ray correlation in the blazar S5 1803+784

Nesci, Roberto; Maselli, A.; Lipunov, V. M.; Martinelli, F.; Siviero, A.; Giroletti, M.; Orienti,, M.

We present a comparison between the optical and Gamma-ray light curves of the Low Frequency Peaked BL Lac object S5 1803+784 since the beginning of the Fermi-LAT mission (August 2008) up to September 2018.
We also considered X-ray data from SWIFT-XRT taken in several pointings between 2009 and 2015, two of them during the 2015 flare. Furthermore we compared a VLBA radio map obtained by us in 2016 with the last available MOJAVE map (November 2012). An optical spectrum was taken during the 2015 flare. The good temporal correlation between optical and Gamma-ray fluxes supports a common origin for the emitting processes in the two energy bands. The smaller variability of the X-ray flux is consistent with an SSC scenario. The MgII 2800 A emission line is not detected during the flare, indicating that the BLR was not involved.
The VLBA map suggests that a radio-emitting blob has been formed after the Gamma-ray flare and is moving along the jet.

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