Simultaneous observations of the blazar PKS2155-304 from Ultra-Violet to TeV energies

TL;DR

This paper reports the first simultaneous multi-wavelength observations of the blazar PKS2155-304 across UV to TeV energies, revealing flux variability and testing different emission models to explain the source's broadband spectrum.

Contribution

It provides a comprehensive multi-instrument dataset and compares synchrotron self-Compton and lepto-hadronic models for the blazar's emission.

Findings

Detected significant X-ray flux variability.

Synchrotron spectrum extends up to 40 keV.

One-zone SSC model fits current data but not previous observations.

Abstract

The results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS2155-304 involving Swift, NuSTAR, Fermi-LAT and H.E.S.S. are reported. The use of these instruments allows us to cover a broad energy range, important for disentangling the different radiative mechanisms. The source, observed from June 2013 to October 2013, was found in a low flux state with respect to previous observations but exhibited highly significant flux variability in the X-rays. The high-energy end of the synchrotron spectrum can be traced up to 40 keV without significant contamination by high-energy emission. A one-zone synchrotron self-Compton model was used to reproduce the broadband flux of the source for all the observations presented here but failed for previous observations made in April 2013. A lepto-hadronic solution was then explored to explain these earlier observational results.