Research output: Contribution to journal › Conference article › peer-review
Activity cycles of blazars and quasars from VLBI observations. / Kudryavtseva, N. A.; Britzen, S.; Aller, M. F.; Aller, H. D.; Gabuzda, D. C.; Jorstad, S. G.; Teräsranta, H.; Witzel, A.; Zensus, J. A.
In: Proceedings of Science, Vol. 72, 008, 2008.Research output: Contribution to journal › Conference article › peer-review
}
TY - JOUR
T1 - Activity cycles of blazars and quasars from VLBI observations
AU - Kudryavtseva, N. A.
AU - Britzen, S.
AU - Aller, M. F.
AU - Aller, H. D.
AU - Gabuzda, D. C.
AU - Jorstad, S. G.
AU - Teräsranta, H.
AU - Witzel, A.
AU - Zensus, J. A.
N1 - Publisher Copyright: © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
PY - 2008
Y1 - 2008
N2 - We discuss a new approach for measuring flaring activity cycles of blazars and quasars. The activity cycles of 21 active galactic nuclei were estimated using the radio total flux-densities at five frequencies (5 GHz-37 GHz) and high resolution long-term very long-baseline interferometry (VLBI) observations (1.6 GHz-43 GHz). We define the activity cycles as the time period between two successive "core" outbursts in the total flux-density radio light curves. The "core" outbursts show frequency-dependent time-delays, flat amplitude spectra and are associated with brightening of the VLBI core. We show that the activity cycles are very long and have durations from 4 to >25 years in observer's frame. We also show that a few sources, such as S5 1803+784, reveal less active behavior if we take into account the long-term VLBI and total flux-density observations for more than 20 years. We found for four sources that core flares appear periodically and that activity cycles coincide with a period in the total flux-density variability. Analysis of the activity cycles leads us to suggest that more massive blazars and quasars possess shorter activity cycles. Quasars and blazars with mass as of about 108 Msun have activity cycles of ∼12 yrs, whereas sources with mass as of 1010 Msun have activity cycles of about 2 yrs in the source frame.
AB - We discuss a new approach for measuring flaring activity cycles of blazars and quasars. The activity cycles of 21 active galactic nuclei were estimated using the radio total flux-densities at five frequencies (5 GHz-37 GHz) and high resolution long-term very long-baseline interferometry (VLBI) observations (1.6 GHz-43 GHz). We define the activity cycles as the time period between two successive "core" outbursts in the total flux-density radio light curves. The "core" outbursts show frequency-dependent time-delays, flat amplitude spectra and are associated with brightening of the VLBI core. We show that the activity cycles are very long and have durations from 4 to >25 years in observer's frame. We also show that a few sources, such as S5 1803+784, reveal less active behavior if we take into account the long-term VLBI and total flux-density observations for more than 20 years. We found for four sources that core flares appear periodically and that activity cycles coincide with a period in the total flux-density variability. Analysis of the activity cycles leads us to suggest that more massive blazars and quasars possess shorter activity cycles. Quasars and blazars with mass as of about 108 Msun have activity cycles of ∼12 yrs, whereas sources with mass as of 1010 Msun have activity cycles of about 2 yrs in the source frame.
UR - http://www.scopus.com/inward/record.url?scp=85055469419&partnerID=8YFLogxK
M3 - Conference article
AN - SCOPUS:85055469419
VL - 72
JO - Proceedings of Science
JF - Proceedings of Science
SN - 1824-8039
M1 - 008
T2 - 9th European VLBI Network Symposium on The role of VLBI in the Golden Age for Radio Astronomy and EVN Users Meeting, EVN Symposium 2008
Y2 - 23 September 2008 through 26 September 2008
ER -
ID: 88377445