Radio Astronomy Division

Colloquium information

Title The Origin and Evolution of the Multi-band Variability in the Radio Source 4C 38.41
DateTime 2018-09-14  15:00~16:00
Place JYS 331-2
Host Sang-Sung Lee
Speaker Juan-Carlos Algaba (Seoul National University)
Abstract We present multi-frequency simultaneous VLBI radio observations of the flat spectrum radio quasar 1633+382 (4C 38.41) as part of the interferometric monitoring of γ-ray-bright active galactic nuclei (iMOGABA) program combined with additional observations in the radio, optical, X-rays, and γ-rays carried out during the period 2012 March–2015 August. The monitoring of this source reveals a significant long-lived increase in its activity for approximately two years in the radio bands, which correlates with a similar increase in all other bands from submillimeter to γ-rays with time lags of ∼70 days, with γ-rays leading radio emission. The epochs of the maxima for the two largest γ-ray flares coincide with the ejection of two respective new VLBI components. The evolution of the flare in the turnover frequency-turnover flux density plane probes the adiabatic losses in agreement with the shock-in-jet model. The derived synchrotron self-absorption magnetic fields, of the order of 0.1mG, do not seem to change dramatically during the flares, and are much weaker, by a factor 104, than the estimated equipartition magnetic fields, indicating that the source of the flare may be associated with a particle-dominated emitting region.
Remarks This talk is also a special KASI colloquium.

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