Particle Acceleration and Magnetic Field Structure in PKS 2155-304: Optical Polarimetric Observations

Abstract

In this paper we present multiband optical polarimetric observations of the VHE blazar PKS 2155-304 made simultaneously with a H.E.S.S./Fermi high-energy campaign in 2008, when the source was found to be in a low state. The intense daily coverage of the dataset allowed us to study in detail the temporal evolution of the emission and we found that the particle acceleration timescales are decoupled from the changes in the polarimetric properties of the source. We present a model in which the optical polarimetric emission originates at the polarised mm-wave core and propose an explanation for the lack of correlation between the photometric and polarimetric fluxes. The optical emission is consistent with an inhomogeneous synchrotron source in which the large scale field is locally organised by a shock in which particle acceleration takes place. Finally, we use these optical polarimetric observations of PKS 2155-304 at a low state to propose an origin for the quiescent gamma-ray flux of the object, in an attempt to provide clues for the source of its recently established persistent TeV emission.

11 pages, 5 figures, accepted for publication in MNRAS

References in corpus (7)

• Multiwaveband Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Correlated Polarization Behavior
• Simultaneous observations of PKS 2155-304 with H.E.S.S., Fermi, RXTE and ATOM: spectral energy distributions and variability in a low state
• VHE gamma-ray emission of PKS 2155-304: spectral and temporal variability
• The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation
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• Testing two-component models on very-high-energy gamma-ray emitting BL Lac objects
• Short Timescale Photometric and Polarimetric Behavior of two BL Lacertae Type Objects
• Probing shock acceleration in BL Lac jets through X-ray polarimetry: the time-dependent view
• Insights into the emission of the blazar 1ES 1011+496 through unprecedented broadband observations during 2011 and 2012
• Polarized synchrotron emission in quiescent black hole X-ray transients
• Time-dependent modelling of PKS 2155-304 in a low state
• Polarimetric Tomography of Blazar Jets
• Impact of seeing and host galaxy into the analysis of photo-polarimetric microvariability in blazars - Case study of the nearby blazars 1ES 1959+650 and HB89 2201+044
• The optical polarization of the blazar PKS 2155$-$304 during an optical flare in 2010
• Optical Photopolarimetry of Blazar OJ287