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IAU Colloquium 164: Radio Emission from Galactic and Extragalactic Compact Sources
ASP Conference Series, Vol. 144, 1998
J. A. Zensus, G. B. Taylor, & J. M. Wrobel (eds.)
Multi­Frequency Monitoring of a Sample of Extragalactic Radio
Sources
M. Mingaliev, A. Botashev, & V. Stolyarov
Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij
Arkhyz, Karachai­Circassian Republic, Russia
Abstract. The preliminary results of monitoring of simultaneous spectra of a sample of
extragalactic sources are given. 1 Eight sets of observations were done at the RATAN­600 radio
telescope in 1995­1996 at six frequencies (0.96, 2.3, 3.9, 7.7, 11.2, and 22 GHz). The light
curves as well as the variability parameters are given.
1. Observations and Data Reduction
This paper presents the preliminary results of a two­year monitoring program at
five­six frequencies. The total number of monitored sources was 66 of different
kind of objects from the extragalactic ``zoo'' (QSO, RG, CSO, BL Lac, Lens
and etc.) and different kind of spectra (flat, GPS, CSS) on Declination range
from ­24 ffi to +44 ffi . During 1995­1996 six­eight sets of observations were done
for most objects from the list.
The observations were done by transit mode at the North sector of the
RATAN­600 radio telescope at 2.7 cm, 3.9 cm, 7.6 cm, 13 cm, and 31 cm (at some
sets we used 1.38 cm receiver too). Usually each source was observed 5­8 times
per set. Scans of all of the sources were corrected for baseline and Gaussians
were fit to the response. The accuracy of flux densities were determined as the
``standard error'' from the N observations of each source during a set.
The calibration sources listed in the next Table were used to convert the
response to janskys:
Table 1. Adopted Calibrator Sources Flux Densities.
Name S1:38 S2:7 S3:9 S7:6 S13 S31
1245\Gamma197 0.63 1.24 1.75 3 4 6.3
0624\Gamma058 1.15 2.76 4.16 8.11 12.8 24.1
0518+165 1.15 2.28 2.91 4.04 6.38 10.1
1328+307 2.49 4.22 5.53 8.57 11.5 17.2
0134+329 1.24 2.5 3.63 6.88 10.9 21.9
2105+420 5.5 6.02 6.33 5 2.6 ­
Notes: NAME: name of the source;S1:38 ; S2:7 ; S3:9 ; S7:6 ; S13 ; S31 : fluxes on corresponding wave­
length in Jy.
For the RATAN­600 radio telescope the antenna gain depends upon source
declination (i. e. elevation above the horizon) as well as upon wavelength, and its
behavior was determined by measuring antenna temperatures at all wavelengths
of sources of known flux density spanning a wide range of declination (see Table
above). On the next Figure 1 one can see typical calibration curve at –=2.7 cm.
1 Figures 2, 3, 4 and Table 2 are available electronically via anonymous ftp on site big1:sao:ru
in directory =data=ratan=variability paper.
279

280 Mingaliev, Botashev, & Stolyarov
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Figure 1. Typical calibration curve of antenna at –=2.7 cm.
These data were found to be well described by gain curves of the form,
g = a \Gamma b \Delta H + c \Delta H 2 ,
where H is the elevation of the source above the horizon. The fitted values of
a, b and c were determined for each sets and each wavelengths.
2. Results
For the time being the main results of this work are available only in the form of
light curves and variability parameters (see Figure 2 and Table 2). In some cases
the error bars on the light curves are greater than might be expected from the
system sensitivity (antenna + receiver). More accurate inspection of data has
shown that it is because of intraday variability (IDV). As an example on Figure
3 one can see the light curves at three wavelengths (– = 2.7 cm, 7.6, and 13 cm)
for the PKS 0528+134. On the next Figure 4 are plotted the – = 13 cm data for
``nonvariable'' sources along with the PKS 0528+134 data from December, 1996
set. During 5--10 days the flux density from this source decreased ú 2 times. All
available data are not yet analyzed for the IDV purpose too.
We expect ``to tie'' these data to other waveband data as well as to VLBI
observations.
Because of lack of space Figures 2--4 and Table 2 with all data
(flux densities and their errors, light curves, derived variability parame­
ters) are available electronically via ftp on site big1:sao:ru in directory
=data=ratan=variability paper.
Acknowledgments. This research has been supported in part by the INTAS Project No
94­4010 and Netherlands Organization for Scientific Research (NWO). MM's participation at
this Meeting was supported by the IAU and by the RFBR (Project No 97­02­26696) Travel
Grants.