Abstract Details
| Name: Sunil Chandra Affiliation: Tata Institute of Fundamental Research, Mumbai Conference ID: ASI2016_394 Title : Synchrotron polarisation and SEDs during high energy flares in blazars Authors and Co-Authors : K. P. Singh Tata Institute of Fundamental Research, Mumbai Markus Böttcher NWU, Potchefstroom, South Africa Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : The blazars are characterised by the non-thermal broadband double-humped Spectral Energy Distribution (SED), with first one peaking at lower energies (submm to X-rays), whereas, the second peak lies in MeV-GeV band. The low energy emission in blazars are contributed by the synchrotron emission by the ultra-relativistic electrons and positrons in the jet. Whereas, the high energy emission is thought to be originated due to either the proton synchrotron, pion decay during hadronic interactions (Hadronic models) or attributed to the Inverse Comptonization (IC) of low energy seed photons in the jet (Leptonic models). A combination of both approaches are also utilised to explain the data, if needed. However, in most of the cases, leptonic models are good approximations for re-generating the observed SEDs in blazars. On the other hand, blazars show high variability, oftenly connected with the high and variable polarisation in the radio & optical bands, parameterised by the Degree of Polarisation (DP) and Position Angle (PA). The rotations or swings in PA are also seen in many high energy flares in blazars. The DP depends on the particle energy distribution, strength and topology of magnetic field. The DP may be significantly diluted with the un-polarized emission from other thermal components of SEDs, namely disk, torus, line-regions, host-galaxies etc. The PA, however, only depends on the topology of local magnetic fields. The polarisation observations, thus may uniquely be used to understand the nature of the magnetic field and the shock, a possible driver for flares in the blazars, if complemented with SEDs. Therefore, a time-dependent modelling of broad-band simultaneously observed SEDs and synchrotron polarisation can be used as a tool to understand these enigmatic systems. The unprecedented capability of ASTROSAT enables us to look for temporal evolution of flux at different parts of the SEDs. Thus, the timing and broad-band spectral studies of these objects may uncover many unseen properties of blazar jet. Few previous results and prospects of the coordinated ASTROSAT+Fermi+ground based platforms shall be discussed during the conference. |