J/A+A/551/A32 Catching the radio flare in CTA 102 (Fromm+, 2013)
Catching the radio flare in CTA 102. II. VLBI kinematic analysis.
Fromm C.M., Ros E., Perucho M., Savolainen T., Mimica P., Kadler M.,
Lobanov A.P., Lister M.L., Kovalev Y.Y., Zensus J.A.
<Astron. Astrophys. 551, A32 (2013)>
=2013A&A...551A..32F 2013A&A...551A..32F (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; VLBI
Keywords: galaxies: active - galaxies: jets - quasars: individual: CTA 102 -
radiation mechanisms: non-thermal - radio continuum: galaxies
Abstract:
Very Long Baseline Interferometry (VLBI) observations can resolve the
radio structure of active galactic nuclei (AGN) and provide estimates
of the structural and kinematic characteristics on parsec-scales in
their jets. The changes in the kinematics of the observed jet features
can be used to study the physical conditions in the innermost regions
of these sources. We performed multifrequency multiepoch Very Long
Baseline Array (VLBA) observations of the blazar CTA102 during its
2006 radio flare, the strongest ever reported for this source. These
observations provide an excellent opportunity to investigate the
evolution of the physical properties of blazars, especially during
these flaring events.
We want to study the kinematic changes in the source during the strong
radio outburst in April 2006 and test the assumption of a shock-shock
interaction. This assumption is based on the analysis and modeling of
the single-dish observations of CTA 102 (Paper I,
2011A&A...531A..95F 2011A&A...531A..95F). In this paper we study the kinematics of CTA 102
at several frequencies using VLBI observations. From the modeled jet
features we derived estimates for the evolution of the physical
parameters, such as the particle density and the magnetic field.
Furthermore ,we combined our observations during the 2006 flare with
long-term VLBA monitoring of the source at 15 GHz and 43 GHz
We cross-identified seven features throughout our entire
multifrequency observations and find evidence of two possible
recollimation shocks around 0.1mas (deprojected 18pc at a viewing
angle of 2.6° and 6.0mas (deprojected 1kpc) from the core. The
43GHz observations reveal a feature ejected at epoch
tej=2005.9±0.2, which could be connected to the 2006 April radio
flare. Furthermore, this feature might be associated with the
traveling component involved in the possible shock-shock interaction,
which gives rise to the observed double peak structure in the
single-dish light curves reported in Paper I, 2011A&A...531A..95F 2011A&A...531A..95F.
Description:
The CTA 102 was observed with all ten antennas of the VLBA, where CTA
102 was the main target within the experiment BR122. In the BS157 and
the BW086 experiment other observations CTA 102 was used as a D-term
calibrator (see below for experiment codes)
--------------------------
code Date (yyyy-mm-dd)
--------------------------
BS157A 2005-05-19
BS157C 2005-09-01
BR122A 2006-04-14
BR122B 2006-06-08
BW086B 2006-10-02
BW086C 2006-12-04
BW086D 2007-01-26
BW086E 2007-04-26
--------------------------
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
22 32 36.42 +11 43 50.8 CTA 102 = 4C 11.69
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea6.dat 41 304 Fitted components for multifrequency
VLBI observations
list.dat 93 40 List of FITS files
fits/* . 40 Individual FITS files
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 GHz nu Frequency ν
4- 13 A10 "YYYY-MM-DD" Date Observation date
15- 18 A4 --- Comp Component ("core" or [ABCD]NN)
20- 23 F4.2 Jy S(nu) ?=- Flux density at Frequency ν
25- 29 F5.2 mas R ?=- Distance from core
31- 36 F6.2 deg theta ?=- Position angle
38- 41 F4.2 mas FWHM ?=- FWHM
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
22- 26 F5.3 mas/pix Scale Scale of the image
28- 31 I4 pix Nx Number of pixels along X-axis
32 A1 --- --- [x]
33- 36 I4 pix Ny Number of pixels along Y-axis
42- 48 F7.4 GHz Freq [4.99/43.22] Frequency
50- 61 A12 --- FileName Name of FITS file in subdirectory fits
63- 72 A10 "Y-M-D" Date Observation date
74- 93 A20 --- Title Title of the file
--------------------------------------------------------------------------------
Acknowledgements:
Christian M. Fromm, cfromm(at)mpifr.de
References:
Fromm et al., Paper I 2011A&A...531A..95F 2011A&A...531A..95F
(End) Christian M. Fromm [MPIfR, Germany], Patricia Vannier [CDS] 29-Jan-2013