A near magnetic-to-kinetic energy equipartition flare from the relativistic jet in AO 0235+164 during 2013-2019

Publication date: 
Main author: 
Cheong, Whee Yeon
IAA authors: 
Agudo, Iván;Fuentes, Antonio;Traianou, Efthalia;Escudero, Juan
Cheong, Whee Yeon;Lee, Sang-Sung;Kim, Sang-Hyun;Kang, Sincheol;Kim, Jae Young;Rani, Bindu;Readhead, Anthony C. S.;Kiehlmann, Sebastian;Lähteenmäki, Anne;Tornikoski, Merja;Tammi, Joni;Ramakrishnan, Venkatessh;Agudo, Iván;Fuentes, Antonio;Traianou, Efthalia;Escudero, Juan;Thum, Clemens;Myserlis, Ioannis;Casadio, Carolina;Gurwell, Mark
Monthly Notices of the Royal Astronomical Society
Publication type: 
We present the multiwavelength flaring activity of the blazar AO 0235+164 during its recent active period from 2013 to 2019. From a discrete correlation function (DCF) analysis, we find a significant ($&gt;95~{{\%}}$) correlation between radio and γ-ray light curves with flares at longer wavelengths following flares at shorter wavelengths. We identify a new jet component in 43 GHz VLBA data that was ejected from the radio core on MJD $57246^{+26}_{-30}$ (2015 August 12), during the peak of the 2015 radio flare. From the analysis of the jet component, we derived a Doppler factor of δ<SUB>var</SUB> = 28.5 ± 8.4, a bulk Lorentz factor of $\Gamma =16.8^{+3.6}_{-3.1}$, and an intrinsic viewing angle of $\theta _{\rm v}=1.42^{+1.07}_{-0.52}\textrm {~degrees}$. Investigation of the quasi-simultaneous radio data revealed a partially absorbed spectrum with the turnover frequency varying in the range of 10 - 70 GHz and the peak flux density varying in the range of 0.7 - 4 Jy. We find the synchrotron self-absorption magnetic field strength to be $B_{\rm SSA}=15.3^{+12.6}_{-14.0}\textrm {~mG}$ at the peak of the 2015 radio flare, which is comparable to the equipartition magnetic field strength of $B_{\rm EQ}=43.6^{+10.6}_{-10.4}\textrm {~mG}$ calculated for the same epoch. Additional analysis of the radio emission region in the relativistic jet of AO 0235+164 suggests that it did not significantly deviate from equipartition during its recent flaring activity.
ADS Bibcode: 
BL Lacertae objects: individual: AO 0235+164;galaxies: active;galaxies: jets;radio continuum: galaxies;Astrophysics - High Energy Astrophysical Phenomena;Astrophysics - Astrophysics of Galaxies