Long-term Optical Polarization Variability and Multiwavelength Analysis of Blazar Mrk 421

Abstract

The results of 8-year R-band photopolarimetric data of blazar Mrk 421 collected from February 2008 to May 2016 are presented, along with extensive multiwavelength observations covering from radio to TeV γ-rays around the flares observed in May 2008, March 2010, and April 2013. The most important results are found in 2013 when the source displayed in the R-band a very high brightness state of 11.29 ± 0.03 mag (93.60 ± 1.53 mJy) on April 10th and a polarization degree of (11.00 ± 0.44)% on May 13th. The analysis of the optical data shows that the polarization variability is due to the superposition of two polarized components that might be produced in two distinct emitting regions. An intranight photopolarimetric variability study carried out over 7 nights after the 2013 April maximum found flux and polarization variations on the nights of April 14, 15, 16 and 19. In addition, the flux shows a minimum variability timescale of ∆ t =2.34±0.12 hours, and that the polarization degree presented variations of ∼ (1 -2) % in a timescale of ∆ t ∼ minutes. Also, a detailed analysis of the intranight data shows a coherence length of the large-scale magnetic field of l B 0.3 pc which is the same order of magnitude to the distance traveled by the relativistic shocks. This result suggests that there is a connection between the intranight polarimetric variations and spatial changes of the magnetic field. Analysis of the complete R-band data along with the historical optical light curve found for this object shows that Mrk 421 varies with a period of 16.26 ± 1.78 years.

Probing an X-Ray Flare Pattern in Mrk 421 Induced by Multiple Stationary Shocks: A Solution to the Bulk Lorentz Factor Crisis

“…It is one of the most monitored blazars in all wavelengths and shows frequent giant flares (e.g. Aleksić et al 2015;Abeysekara et al 2017;Fraija et al 2017). Mrk 421 is perfectly adapted for this study by also presenting 4 well-defined VLBI quasi-stationary knots within 5 mas of the radio core at 15.3 GHz, as shown in Figure 2 (Left) from the MOJAVE collaboration.…”

Optical polarization properties of February 2010 outburst of the blazar Mrk 421

“…The flaring activity was detected to be dominant in the X-ray and γ-ray energy bands. A summary of the nature of optical linear polarization obtained from the present study is given in the following points: (Fraija et al 2017). This explains the the long-term quiescent state of the source in optical bands.…”

“…The degree of linear polarization (Π linear ) for optically thin synchrotron radiation depends on the photon spectral index (energy distribution of electrons) and structure of the magnetic field. It is expressed as (Westfold 1959;Björnsson 1985;Fraija et al 2017)…”

Optical Polarimetric and Multiwavelength Flaring Activity of Blazar 3C 279

“…A single beam polarimeter so-called POLIMA 2 was used. Details on calibration, data reduction, the correction due to host galaxy contribution and the conversion between R-band magnitudes and fluxes are shown in Sorcia et al (2013Sorcia et al ( , 2014; Fraija et al (2017b). Figure 1 shows the long-term R-band photopolarimetric Jermak et al 2016;Marscher et al 2010), and also due to turbulent magnetic field resulting in a random direction of the polarization vector (Jones et al 1985;Marscher 2014).…”

“…In the optical bands, polarization variations have been observed also in timescales ranging from some minutes (see, e.g. Bhatta et al 2015;Fraija et al 2017b) and also, large rotations of the electric vector position angle (EVPA) have been reported during flaring activities (see, e.g. Sorcia et al 2014;Kiehlmann et al 2016).…”