DA 55 (0133+476): This HPQ source has been monitored in Metsahovi for over 20
years at 22 and 37 GHz and for almost 15 years at 90 GHz. It has shown high
apparent pattern velocity of 18c in the jet (Piner et al. 2007) and has been
also a target of many other studies using Very Long Baseline Interferometry
(VLBI) observations (e.g. Kellermann et al. 2004; Lister & Homan 2005; Lister
2001). It is also included in the wavelet study of Kelly et al. (2003) which
uses the UMRAO 4.8, 8, 14.5 GHz monitoring data. They found a timescale of 2.3
years for the source at 14.5 GHz. This is very close to the timescale of 2.2
years which we obtained for the source at both 22 and 37 GHz. At 90 GHz we only
found a flare timescale of 0.7 years for the source. The long-term timescale in
our analysis has a rising trend so that it is shortening towards a peak of a
large flare. The timescale is present only for about 40% of the flux curve at
both 22 and 37 GHz but still has repeated 4.4 times at both of the frequency
bands. In Paper I we could not find any DCF or periodogram timescale for the
source. When the flux curve is examined we can clearly see that the timescale
obtained here is related to a period when the source had many similar flares and
the total flux level rises. This also explains the rising trend in the wavelet
plot which is caused by more frequent individual flares towards the peak of the
Most of the emission is in a small, central component. The emission
to the north is strong at low frequencies, and the component to the
northwest is stronger at high frequencies. The VLBA2cm1 observations
show this northwest component decreasing in flux density with time.
3.1. B0133+476 This quasar exhibits a relatively high RM of
1420 +- 56 rad m^-2^ in the core (Fig. 1). The percent polarization
increases at the location of the fit from 1.3% at 15 GHz to 1.9% at
8.1 GHz. The extension northwest of the core with a positive RM of
40 +- 90 rad m^-2^ is consistent with an RM of zero. There is therefore
no convincing evidence for a change of sign of the B field in this
region. This region does coincide with an optically thin spectrum from
8 to 12 GHz, as indicated in Figure 2. The core has a flat spectrum
across these frequencies.
0133+476.-There is no evidence of any large-scale structure in this
object (Kapahi 1981; Perley 1982). Perley's observations place an
upper limit of 0.2 mJy on any structure in the range 0.2"-6", and they
show that the level of polarization is 1.5 % at both 1.4 and 5 GHz.
Altschuler (1980) observed a significant rotation in the
polarization position angle at 8 GHz during a radio outburst. The source
is strongly variable on a time scale of months (Andrew et al. 1978;
Seielstad, Pearson, and Readhead 1983). VLBI observations at 5 and 15 GHz
(Weiler and Johnston 1980) yielded a visibility of 0.7 between Green
Bank and Effelsberg, indicating a size of 0.7 mas. There is also some
evidence in their observations for an elongation in P.A. 140deg.
Marscher and Shaffer (1980) made VLBI observations at 1.7 and 10 GHz;
at 1.7 GHz, an elliptical Gaussian model with FWHM 5 mas x 2 mas
elongated in P.A. 170deg fits well and accounts for all of the flux
density of the source; at 10 GHz, an elliptical Gaussian with FWHM
0.8 mas x 0.5 mas elongated in P.A. 123deg fits well.
In our observations the closure phases indicate that the object is
resolved and asymmetric. A two-component model fits the data well, and
shows that there is a resolved component northwest of the unresolved
core. A slightly better fit is obtained with the three-component model
given in Table 4, which indicates larger structure extending about 10
mas to the west.
Where necessary, we have assumed H_0_ = 100h km s^-1^ Mpc^-1^
and q_0_ = 0.5 to convert angles to projected distances.