Speaker
Ulisses Barres
(Centro Brasileiro de Pesquisas Físicas)
Description
n 2012, Fermi/LAT gamma-ray and radio observations have registered the largest ever recorded flaring episodes from the blazar Markarian 421.
The unprecedented activity state of the source has remained high, and much above the normal behaviour seem from the source also for the year 2013, characterising a dramatic and long-lasting change of behaviour in the emission of the object. This unique event has been followed, and showed extreme signatures in all bands in which it was observed, from radio to VHE gamma-rays. Polarisation monitoring of the source has nevertheless been somewhat more scarce, and direct observation of the peak activity in 2012 was prevented by the source's proximity with the Sun at the time.
As part of our continuous monitoring programme of TeV emitting blazars in optical polarimetry at the Liverpool Telescope, whose first phase used the RINGO2 fast polarimeter and lasted from late 2010 to early 2013, we have observed Mkn 421 with regular coverage and a sub-weekly cadence for over two years. This continued monitoring allowed us to follow the polarisation behaviour of the source for over two years and up to the days preceding the dramatic flare event in 2012. In the weeks before the multi-wavelength and high-energy outbursts, Mrk 421 presented an unprecedented increase in its degree of polarisation, which rose by a factor of 5, not witnessed in decades from this object. The source also showed a never-seen large rotation of its polarisation angle, by over 180 degrees. In this talk we will present our entire dataset on Mkn 421 , concentrating in discussing the unprecedented events in optical polarisation that preceded the HE outburst. The main question we put ourselves is if what we have seen is a polarimetric precursor of the high activity that followed. If yes, what connections can we establish between them, and what remains mysterious to us about it?
| Registration number following "ICRC2015-I/" | 0543 |
|---|---|
| Collaboration | -- not specified -- |
Primary author
Ulisses Barres
(Centro Brasileiro de Pesquisas Físicas)
Co-authors
Prof.
Carole Mundell
(Liverpool John Moores University)
Elina Lindfors
(University of Turku)
Helen Jermak
(Liverpool John Moores University)
Prof.
Iain Steele
(Liverpool John Moores University)
Dr
Kari Nilsson
(Tuorla Observatory)
