Variability of Blazar ”NRAO512”

【日時】5月14日(水) 10:30-12:00
【タイトル】Variability of Blazar ”NRAO512”
【発表者(敬称略)】貴島政親(総研大 D3・水沢、指導教員 川口則幸)
Blazars are very compact and highly variable sources.
According to unification scheme, they have a relativistic jet that is pointing in the general direction of the Earth.
They were divided into two sub-classes ”BL Lacetae Objects (hereafter”BLO”)”
and ”Flat-Spectrum Radio Quasar (hereafter ”FSRQ”)”.
The primary difference is that BLO has no(or weak) emission line, FSRQ has strong emission line. Many authors have attempted
to explain their differences in terms of evolution(FSRQ into BLO) or beaming effect or others. Discussion have been continued over 15-20yr, and haven’t completed yet.
Authors have reported many studies on flux variability of AGN , however their periodicities have been still unclear. Only OJ287 shows
the clear evidence of 12 yr periodicity. The origin of variability have been investigated using VLBI. According to recent publications,
there are two kinds of flare which has freq-lag ”core-flare” and no freq-lag ”jet-flare”.
Pyatunina et al.(2000,2007) defined the activity cycle as the time interval between two successive ”core (optically thick) flare”. Between 2000 and 2007, they found periodicities of flux variations for 6 sources, and investigated the origin of variation using VLBI mapping technique.
I found that the Blazar ”NRAO512” flared in 2007/06 using Japanese eVLBI-array ”OCTAVE”. Above-menthioned, periodicity of flare
is important. I analyzed over 100 epoch archives of VLBI. I found the periodicity of flux variation for Blazar ”NRAO512”. The periodicity is 9-10 yr.
This result is important to support existence of periodicity.
Because ”NRAO512” is very compact source, many authors could not determine the orientation of jet and their structure
using VLBI with 2 milli-arcsecond resolution. I analyzed more higher resolution (less than 1 mas) datum, and first determined the orientation and proper motion of jet knot.
Finally, I introduce a new hypothesis that the period of variability may be a good tool to investigate difference between BLO and FSRQ.