A1 Refereed original research article in a scientific journal
Multifrequency study of the gamma-ray flaring BL Lacertae object PKS 2233-148 in 2009-2012
Authors: A. B. Pushkarev, M. S. Butuzova, Y. Y. Kovalev, T. Hovatta
Publisher: OXFORD UNIV PRESS
Publication year: 2019
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 482
Issue: 2
First page : 2336
Last page: 2353
Number of pages: 18
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/sty2724
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/39604214
We study the jet physics of the BL Lacertae object PKS 2233-148, making use of the synergy of observational data sets in the radio and gamma-ray energy domains. The four-epoch multifrequency (4-43 GHz) very-long-baseline array (VLBA) observations focused on the parsec-scale jet were triggered by a flare in gamma-rays registered by Fermi-LAT on 2010 April 23. We also used 15-GHz data from the OVRO 40-m telescope and MOJAVE VLBA monitoring programs. The jet shape of the source is found to be conical on scales probed by the VLBA observations, setting a lower limit of about 0.1 on its unknown redshift. Nuclear opacity is dominated by synchrotron self-absorption, with a wavelength-dependent core shift of r(core) ([mas]) approximate to 0.1 lambda[cm] mas co-aligned with the innermost jet direction. The turnover frequency of the synchrotron spectrum of the very-long-baseline interferometry core shifts towards lower frequencies as the flare propagates down the jet, and the speed of this propagation is significantly higher, about 1.2 mas yr(-1), than results from traditional kinematics based on tracking bright jet features. We have found indications that the gamma-ray production zone in the source is located at large distances, 10-20 pc, from a central engine, and could be associated with the stationary jet features. These findings favour synchrotron self-Compton, possibly in combination with external Compton scattering by infrared seed photons from a slow sheath of the jet, as the dominant high-energy emission mechanism of the source.
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