N. Mankuzhiyil

Polarimetric tomography of blazar jets

In this paper we propose a way to use optical polarisation observations to provide independent constraints and guide to the modelling of the spectral energy distribution (SED) of blazars, which is particularly useful when two-zone models are required to fit the observed SED. As an example, we apply the method to the 2008 multiwavelength campaign of PKS 2155-304, for which the required polarisation information was already available. We find this approach succesful in being able to simultaneously describe the SED and variability of the source, otherwise difficult to interpret. More generally, by using polarisation data to disentangle different active regions within the source, the method reveals otherwise unseen correlations in the multiwavelength behaviour which are key for the SED modelling.

Challenging the one zone SSC model in VHE gamma ray emitting BL lacs: The interesting case of PKS 1424+240

The BL Lac object PKS 1424+240 with uncertain redshift has been investigated by the MAGIC imaging atmospheric Cherenkov telescopes at very high energies (VHE; E> 100 GeV) since 2006. The source was observed in various emission states and the integral flux above 150 GeV shows hints of variability. We present a detailed analysis of the multi-frequency emission, from radio to VHE gamma rays. We show that a simple one-zone synchrotron self Compton (SSC) model is inadequate to account for the observed spectral behavior. In particular, the synchrotron peak is much broader than the high-energy peak and the separation between the two peaks is large, which requires high Doppler factor for modeling. We investigate the correlation between lightcurves in several wavebands and propose a two-zone SSC model to fit the experimental data where part of the observed emission is due to a parsec scale jet and the remaining part to a more compact region close to the central engine.

Clues on high-energy emission mechanism from blazar 3C 454.3 during 2015 August flare

We perform a detailed spectral study of a recent flaring activity from the Flat Spectrum Radio Quasar (FSRQ), 3C,454.3, observed simultaneously in optical, UV, X-ray and

Log-normal flux distribution of bright Fermi blazars.

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